diff --git a/src/n8n-service.ts b/src/n8n-service.ts
index 7cc27b9..6b32425 100644
--- a/src/n8n-service.ts
+++ b/src/n8n-service.ts
@@ -75,7 +75,7 @@ JSON:`;
       };
     }
   } catch (error) {
-    console.error('Intent analysis error:', error);
+    logger.error('Intent analysis error', error as Error);
   }
 
   // 기본값: 일반 대화
@@ -114,7 +114,12 @@ export async function callN8n(
     });
 
     if (!response.ok) {
-      console.error('n8n error:', response.status, await response.text());
+      const errorText = await response.text();
+      logger.error('n8n API error', new Error(`Status ${response.status}: ${errorText}`), {
+        status: response.status,
+        userId,
+        type
+      });
       return { error: `n8n 호출 실패 (${response.status})` };
     }
 
@@ -128,7 +133,7 @@ export async function callN8n(
 
     return parseResult.data;
   } catch (error) {
-    console.error('n8n fetch error:', error);
+    logger.error('n8n fetch error', error as Error, { userId, type });
     return { error: 'n8n 연결 실패' };
   }
 }
diff --git a/src/routes/api.ts b/src/routes/api.ts
index 6345d5a..dd5ed03 100644
--- a/src/routes/api.ts
+++ b/src/routes/api.ts
@@ -1,6 +1,7 @@
 import { z } from 'zod';
 import { Hono } from 'hono';
 import { cors } from 'hono/cors';
+import { createMiddleware } from 'hono/factory';
 import { Env } from '../types';
 import { sendMessage } from '../telegram';
 import {
@@ -44,17 +45,20 @@ const ChatApiBodySchema = z.object({
 });
 
 /**
- * API Key 인증 검증 (Timing-safe comparison으로 타이밍 공격 방지)
- * @returns 인증 실패 시 Response, 성공 시 null
+ * API Key 인증 미들웨어 (Timing-safe comparison으로 타이밍 공격 방지)
+ * X-API-Key 헤더로 DEPOSIT_API_SECRET 검증
  */
-function requireApiKey(request: Request, env: Env): Response | null {
-  const apiSecret = env.DEPOSIT_API_SECRET;
-  const authHeader = request.headers.get('X-API-Key');
+const apiKeyAuth = createMiddleware<{ Bindings: Env }>(async (c, next) => {
+  const apiSecret = c.env.DEPOSIT_API_SECRET;
+  const authHeader = c.req.header('X-API-Key');
+
   if (!apiSecret || !timingSafeEqual(authHeader, apiSecret)) {
-    return Response.json({ error: 'Unauthorized' }, { status: 401 });
+    logger.warn('API Key 인증 실패', { hasApiKey: !!authHeader });
+    return c.json({ error: 'Unauthorized' }, 401);
   }
-  return null;
-}
+
+  return await next();
+});
 
 /**
  * CORS 헤더 생성
@@ -101,17 +105,12 @@ async function getOrCreateUser(
 /**
  * GET /api/deposit/balance - 잔액 조회 (namecheap-api 전용)
  *
- * @param request - HTTP Request
  * @param env - Environment bindings
  * @param url - Parsed URL
  * @returns JSON response with balance
  */
-async function handleDepositBalance(request: Request, env: Env, url: URL): Promise<Response> {
+async function handleDepositBalance(env: Env, url: URL): Promise<Response> {
   try {
-    // API Key 인증
-    const authError = requireApiKey(request, env);
-    if (authError) return authError;
-
     const telegramId = url.searchParams.get('telegram_id');
     if (!telegramId) {
       return Response.json({ error: 'telegram_id required' }, { status: 400 });
@@ -150,10 +149,6 @@ async function handleDepositBalance(request: Request, env: Env, url: URL): Promi
  */
 async function handleDepositDeduct(request: Request, env: Env): Promise<Response> {
   try {
-    // API Key 인증
-    const authError = requireApiKey(request, env);
-    if (authError) return authError;
-
     // JSON 파싱 (별도 에러 핸들링)
     let jsonData: unknown;
     try {
@@ -869,14 +864,14 @@ api.use('/contact', cors({
   allowHeaders: ['Content-Type'],
 }));
 
-// GET /deposit/balance - 잔액 조회 (namecheap-api 전용)
-api.get('/deposit/balance', async (c) => {
+// GET /deposit/balance - 잔액 조회 (namecheap-api 전용, API Key 필요)
+api.get('/deposit/balance', apiKeyAuth, async (c) => {
   const url = new URL(c.req.url);
-  return await handleDepositBalance(c.req.raw, c.env, url);
+  return await handleDepositBalance(c.env, url);
 });
 
-// POST /deposit/deduct - 잔액 차감 (namecheap-api 전용)
-api.post('/deposit/deduct', async (c) => {
+// POST /deposit/deduct - 잔액 차감 (namecheap-api 전용, API Key 필요)
+api.post('/deposit/deduct', apiKeyAuth, async (c) => {
   return await handleDepositDeduct(c.req.raw, c.env);
 });
 
diff --git a/src/routes/handlers/message-handler.ts b/src/routes/handlers/message-handler.ts
index 51f40c2..fc0aa38 100644
--- a/src/routes/handlers/message-handler.ts
+++ b/src/routes/handlers/message-handler.ts
@@ -4,8 +4,11 @@ import { handleCommand } from '../../commands';
 import { UserService } from '../../services/user-service';
 import { ConversationService } from '../../services/conversation-service';
 import { ERROR_MESSAGES } from '../../constants/messages';
+import { createLogger } from '../../utils/logger';
 import type { Env, TelegramUpdate } from '../../types';
 
+const logger = createLogger('message-handler');
+
 /**
  * 메시지 처리 핸들러
  */
@@ -44,7 +47,7 @@ export async function handleMessage(
       message.from.username
     );
   } catch (dbError) {
-    console.error('[handleMessage] 사용자 DB 오류:', dbError);
+    logger.error('사용자 DB 오류', dbError as Error, { telegramUserId });
     await sendMessage(
       env.BOT_TOKEN,
       chatId,
@@ -80,7 +83,7 @@ export async function handleMessage(
           await sendMessage(env.BOT_TOKEN, chatId, result.message);
           return;
         } catch (error) {
-          console.error('[handleMessage] 서버 삭제 처리 오류:', error);
+          logger.error('서버 삭제 처리 오류', error as Error, { orderId: JSON.parse(deleteSessionData).orderId });
           await sendMessage(
             env.BOT_TOKEN,
             chatId,
@@ -107,7 +110,7 @@ export async function handleMessage(
           return;
         }
       } catch (error) {
-        console.error('[handleMessage] 삭제 세션 취소 오류:', error);
+        logger.error('삭제 세션 취소 오류', error as Error, { telegramUserId });
       }
     }
 
@@ -202,7 +205,7 @@ export async function handleMessage(
           );
           return;
         } catch (error) {
-          console.error('[handleMessage] 서버 신청 처리 오류:', error);
+          logger.error('서버 신청 처리 오류', error as Error, { telegramUserId });
           await sendMessage(
             env.BOT_TOKEN,
             chatId,
@@ -248,7 +251,7 @@ export async function handleMessage(
 
     // 10. 응답 전송 (키보드 포함 여부 확인)
     if (result.keyboardData) {
-      console.log('[Webhook] Keyboard data received:', result.keyboardData.type);
+      logger.info('Keyboard data received', { type: result.keyboardData.type });
       if (result.keyboardData.type === 'domain_register') {
         const { domain, price } = result.keyboardData;
         const callbackData = `domain_reg:${domain}:${price}`;
@@ -272,7 +275,7 @@ export async function handleMessage(
         ]);
       } else {
         // TypeScript exhaustiveness check - should never reach here
-        console.warn('[Webhook] Unknown keyboard type:', (result.keyboardData as { type: string }).type);
+        logger.warn('Unknown keyboard type', { type: (result.keyboardData as { type: string }).type });
         await sendMessage(env.BOT_TOKEN, chatId, finalResponse);
       }
     } else {
@@ -280,7 +283,7 @@ export async function handleMessage(
     }
 
   } catch (error) {
-    console.error('[handleMessage] 처리 오류:', error);
+    logger.error('처리 오류', error as Error, { chatId, telegramUserId });
     await sendMessage(
       env.BOT_TOKEN,
       chatId,
diff --git a/src/routes/webhook.ts b/src/routes/webhook.ts
index b6bb823..74c302f 100644
--- a/src/routes/webhook.ts
+++ b/src/routes/webhook.ts
@@ -2,6 +2,9 @@ import type { Env } from '../types';
 import { validateWebhookRequest } from '../security';
 import { handleCallbackQuery } from './handlers/callback-handler';
 import { handleMessage } from './handlers/message-handler';
+import { createLogger } from '../utils/logger';
+
+const logger = createLogger('webhook');
 
 /**
  * Telegram Webhook 요청 처리
@@ -10,7 +13,7 @@ export async function handleWebhook(request: Request, env: Env): Promise<Respons
   const validation = await validateWebhookRequest(request, env);
 
   if (!validation.valid) {
-    console.error('[Webhook] 검증 실패:', validation.error);
+    logger.error('검증 실패', new Error(validation.error || 'Unknown validation error'));
     return new Response(validation.error, { status: 401 });
   }
 
@@ -25,7 +28,7 @@ export async function handleWebhook(request: Request, env: Env): Promise<Respons
     await handleMessage(env, update);
     return new Response('OK');
   } catch (error) {
-    console.error('[Webhook] 메시지 처리 오류:', error);
+    logger.error('메시지 처리 오류', error as Error);
     return new Response('Error', { status: 500 });
   }
 }
\ No newline at end of file
diff --git a/src/services/deposit-matcher.ts b/src/services/deposit-matcher.ts
index 4bc315b..e0aad55 100644
--- a/src/services/deposit-matcher.ts
+++ b/src/services/deposit-matcher.ts
@@ -55,11 +55,18 @@ export async function matchPendingDeposit(
   }>();
 
   if (!pendingTx) {
-    console.log('[matchPendingDeposit] 매칭되는 pending 거래 없음');
+    logger.info('매칭되는 pending 거래 없음', {
+      depositorName: notification.depositorName.slice(0, 7),
+      amount: notification.amount
+    });
     return null;
   }
 
-  console.log('[matchPendingDeposit] 매칭 발견:', pendingTx);
+  logger.info('매칭 발견', {
+    transactionId: pendingTx.id,
+    userId: pendingTx.user_id,
+    amount: pendingTx.amount
+  });
 
   try {
     // Optimistic Locking으로 동시성 안전한 매칭 처리
@@ -108,7 +115,7 @@ export async function matchPendingDeposit(
       });
     });
 
-    console.log('[matchPendingDeposit] 매칭 완료:', {
+    logger.info('매칭 완료', {
       transactionId: pendingTx.id,
       userId: pendingTx.user_id,
       amount: pendingTx.amount,
@@ -125,8 +132,12 @@ export async function matchPendingDeposit(
         transactionId: pendingTx.id,
         userId: pendingTx.user_id,
       });
+    } else {
+      logger.error('DB 업데이트 실패', error as Error, {
+        transactionId: pendingTx.id,
+        userId: pendingTx.user_id,
+      });
     }
-    console.error('[matchPendingDeposit] DB 업데이트 실패:', error);
     throw error;
   }
 }
diff --git a/src/utils/circuit-breaker.ts b/src/utils/circuit-breaker.ts
index 5ac7830..4fd280d 100644
--- a/src/utils/circuit-breaker.ts
+++ b/src/utils/circuit-breaker.ts
@@ -1,5 +1,8 @@
 import { metrics } from './metrics';
 import { notifyAdmin, NotificationOptions } from '../services/notification';
+import { createLogger } from './logger';
+
+const logger = createLogger('circuit-breaker');
 
 /**
  * Circuit Breaker pattern implementation
@@ -99,7 +102,7 @@ export class CircuitBreaker {
     this.serviceName = options?.serviceName ?? 'unknown';
     this.notification = options?.notification;
 
-    console.log('[CircuitBreaker] Initialized', {
+    logger.info('Initialized', {
       serviceName: this.serviceName,
       failureThreshold: this.failureThreshold,
       resetTimeoutMs: this.resetTimeoutMs,
@@ -146,7 +149,7 @@ export class CircuitBreaker {
    * Manually reset the circuit to closed state
    */
   reset(): void {
-    console.log('[CircuitBreaker] Manual reset');
+    logger.info('Manual reset', { service: this.serviceName });
     this.state = CircuitState.CLOSED;
     this.failures = [];
     this.openedAt = null;
@@ -178,7 +181,10 @@ export class CircuitBreaker {
       const elapsed = now - this.openedAt;
 
       if (elapsed >= this.resetTimeoutMs) {
-        console.log('[CircuitBreaker] Reset timeout reached, transitioning to HALF_OPEN');
+        logger.info('Reset timeout reached, transitioning to HALF_OPEN', {
+          service: this.serviceName,
+          elapsedMs: elapsed
+        });
         this.state = CircuitState.HALF_OPEN;
 
         // 상태 메트릭 기록 (HALF_OPEN)
@@ -194,7 +200,9 @@ export class CircuitBreaker {
     this.successCount++;
 
     if (this.state === CircuitState.HALF_OPEN) {
-      console.log('[CircuitBreaker] Half-open test succeeded, closing circuit');
+      logger.info('Half-open test succeeded, closing circuit', {
+        service: this.serviceName
+      });
       this.state = CircuitState.CLOSED;
       this.failures = [];
       this.openedAt = null;
@@ -218,7 +226,10 @@ export class CircuitBreaker {
 
     // If in half-open state, one failure reopens the circuit
     if (this.state === CircuitState.HALF_OPEN) {
-      console.log('[CircuitBreaker] Half-open test failed, reopening circuit');
+      logger.warn('Half-open test failed, reopening circuit', {
+        service: this.serviceName,
+        error: error.message
+      });
       this.state = CircuitState.OPEN;
       this.openedAt = now;
 
@@ -246,9 +257,11 @@ export class CircuitBreaker {
     // Check if we should open the circuit
     if (this.state === CircuitState.CLOSED) {
       if (this.failures.length >= this.failureThreshold) {
-        console.log(
-          `[CircuitBreaker] Failure threshold (${this.failureThreshold}) exceeded, opening circuit`
-        );
+        logger.warn('Failure threshold exceeded, opening circuit', {
+          service: this.serviceName,
+          failureThreshold: this.failureThreshold,
+          currentFailures: this.failures.length
+        });
         this.state = CircuitState.OPEN;
         this.openedAt = now;
 
@@ -291,7 +304,9 @@ export class CircuitBreaker {
         'Circuit breaker is open - service unavailable',
         this.state
       );
-      console.log('[CircuitBreaker] Request blocked - circuit is OPEN');
+      logger.warn('Request blocked - circuit is OPEN', {
+        service: this.serviceName
+      });
       throw error;
     }
 
@@ -315,10 +330,11 @@ export class CircuitBreaker {
       this.onFailure(err);
 
       // Log failure
-      console.error(
-        `[CircuitBreaker] Operation failed (${this.failures.length}/${this.failureThreshold} failures):`,
-        err.message
-      );
+      logger.error('Operation failed', err, {
+        service: this.serviceName,
+        failures: this.failures.length,
+        threshold: this.failureThreshold
+      });
 
       // Re-throw the original error
       throw err;
diff --git a/src/utils/retry.ts b/src/utils/retry.ts
index 998b91f..3de4a01 100644
--- a/src/utils/retry.ts
+++ b/src/utils/retry.ts
@@ -12,6 +12,9 @@
 
 import { metrics } from './metrics';
 import { notifyAdmin, NotificationOptions } from '../services/notification';
+import { createLogger } from './logger';
+
+const logger = createLogger('retry');
 
 /**
  * Configuration options for retry behavior
@@ -123,7 +126,11 @@ export async function retryWithBackoff<T>(
 
       // Log success if this was a retry
       if (attempt > 0) {
-        console.log(`[Retry] Success on attempt ${attempt + 1}/${maxRetries + 1}`);
+        logger.info('Success on retry', {
+          service: serviceName,
+          attempt: attempt + 1,
+          totalAttempts: maxRetries + 1
+        });
       }
 
       return result;
@@ -132,10 +139,10 @@ export async function retryWithBackoff<T>(
 
       // If this was the last attempt, throw RetryError
       if (attempt === maxRetries) {
-        console.error(
-          `[Retry] All ${maxRetries + 1} attempts failed. Last error:`,
-          lastError.message
-        );
+        logger.error('All attempts failed', lastError, {
+          service: serviceName,
+          totalAttempts: maxRetries + 1
+        });
 
         // Send admin notification if configured
         if (notification) {
@@ -176,10 +183,13 @@ export async function retryWithBackoff<T>(
         jitter
       );
 
-      console.log(
-        `[Retry] Attempt ${attempt + 1}/${maxRetries + 1} failed. Retrying in ${delay}ms...`,
-        lastError.message
-      );
+      logger.warn('Attempt failed, retrying', {
+        service: serviceName,
+        attempt: attempt + 1,
+        totalAttempts: maxRetries + 1,
+        delayMs: delay,
+        error: lastError.message
+      });
 
       // Wait before next retry
       await sleep(delay);