diff --git a/payments/mixins.py b/payments/mixins.py
index c0cfbe8..6378e8d 100644
--- a/payments/mixins.py
+++ b/payments/mixins.py
@@ -141,12 +141,17 @@ def validate_order(self, order):
             raise ValidationError("결제 가능한 상태의 주문이 아닙니다.")
         if order.get_total_price() > 50000:
             raise ValidationError("결제 금액이 50,000원을 초과할 수 없습니다.")
-        if order.payments.filter(payment_status__in=["completed", "pending"]).exists():
-            raise ValidationError("이미 결제가 완료되었거나 진행 중인 주문입니다.")
 
     def create_payment(self, order, user):
         self.validate_order(order)
 
+        existing_payments = Payment.objects.filter(
+            order=order, payment_status="pending"
+        )
+        if existing_payments.exists():
+            # 모든 기존 pending payment를 취소 처리
+            existing_payments.update(payment_status="cancelled")
+
         try:
             kakao_response = self.kakao_pay_service.request_payment(order)
         except Exception as e:
diff --git a/payments/views.py b/payments/views.py
index 5db952a..b37f78e 100644
--- a/payments/views.py
+++ b/payments/views.py
@@ -265,7 +265,12 @@ def get_queryset(self):
 
     @transaction.atomic
     def post(self, request):
-        order = self.get_queryset().filter(order_status="pending").select_for_update().first()
+        order = (
+            self.get_queryset()
+            .filter(order_status="pending")
+            .select_for_update()
+            .first()
+        )
         if not order:
             return Response(
                 {"detail": "진행 중인 주문이 없습니다."},
@@ -302,23 +307,16 @@ def get(self, request):
                 status=status.HTTP_404_NOT_FOUND,
             )
 
-        # 가장 최근의 pending payment를 가져오고 나머지는 취소 처리
-        payments = list(
-            Payment.objects.filter(order=order, payment_status="pending").order_by(
-                "-created_at"
-            )
+        payment = (
+            Payment.objects.filter(order=order, payment_status="pending")
+            .order_by("-created_at")
+            .first()
         )
-        if not payments:
+        if not payment:
             return Response(
                 {"detail": "해당 주문에 대한 대기 중인 결제를 찾을 수 없습니다."},
                 status=status.HTTP_404_NOT_FOUND,
             )
-        payment = payments[0]
-        # 가장 최근의 pending payment를 제외한 나머지 payment를 취소 처리
-        if len(payments) > 1:
-            Payment.objects.filter(id__in=[p.id for p in payments[1:]]).update(
-                payment_status="cancelled"
-            )
 
         result = request.GET.get("result")
         pg_token = request.GET.get("pg_token")