diff --git a/docs/architecture/transaction-sequence.md b/docs/architecture/transaction-sequence.md
new file mode 100644
index 0000000..996073f
--- /dev/null
+++ b/docs/architecture/transaction-sequence.md
@@ -0,0 +1,26 @@
+```mermaid
+sequenceDiagram
+    participant User
+    participant Controller
+    participant Service
+    participant Repository
+    participant PaymentGateway
+
+    User->>Controller: 결제 요청
+    Controller->>Service: 결제 처리 요청
+    Service->>Repository: 트랜잭션 시작
+    alt 정상 흐름
+        Service->>PaymentGateway: 결제 요청
+        PaymentGateway-->>Service: 결제 성공
+        Service->>Repository: 트랜잭션 커밋
+    else 외부 실패
+        Service->>PaymentGateway: 결제 요청
+        PaymentGateway-->>Service: 결제 실패
+        Service->>Repository: 트랜잭션 롤백
+    else DB 실패
+        Service->>Repository: 트랜잭션 시작
+        Repository-->>Service: DB 오류
+        Service->>Repository: 트랜잭션 롤백
+    end
+    Controller-->>User: 결제 결과 반환
+```
\ No newline at end of file