diff --git a/app/Services/WorkOrderService.php b/app/Services/WorkOrderService.php
index 692048d..50717b5 100644
--- a/app/Services/WorkOrderService.php
+++ b/app/Services/WorkOrderService.php
@@ -576,8 +576,8 @@ public function updateStatus(int $id, string $status, ?array $resultData = null)
                     // Fast-track 완료의 경우 started_at도 설정 (중간 상태 생략)
                     $workOrder->started_at = $workOrder->started_at ?? now();
                     $workOrder->completed_at = now();
-                    // 모든 품목에 결과 데이터 저장
-                    $this->saveItemResults($workOrder, $resultData, $userId);
+                    // 모든 품목에 결과 데이터 저장 (LOT 번호 반환)
+                    $lotNo = $this->saveItemResults($workOrder, $resultData, $userId);
                     break;
                 case WorkOrder::STATUS_SHIPPED:
                     $workOrder->shipped_at = now();
@@ -604,7 +604,14 @@ public function updateStatus(int $id, string $status, ?array $resultData = null)
                 $this->stockInFromProduction($workOrder);
             }
 
-            return $workOrder->load(['assignee:id,name', 'assignees.user:id,name', 'team:id,name', 'process:id,process_name,process_code']);
+            $result = $workOrder->load(['assignee:id,name', 'assignees.user:id,name', 'team:id,name', 'process:id,process_name,process_code']);
+
+            // 완료 시 LOT 번호를 응답에 포함
+            if (isset($lotNo)) {
+                $result->setAttribute('lot_no', $lotNo);
+            }
+
+            return $result;
         });
     }
 
@@ -1106,7 +1113,7 @@ private function autoStartWorkOrderOnMaterialInput(WorkOrder $workOrder, int $te
     /**
      * 작업지시 품목에 결과 데이터 저장
      */
-    private function saveItemResults(WorkOrder $workOrder, ?array $resultData, int $userId): void
+    private function saveItemResults(WorkOrder $workOrder, ?array $resultData, int $userId): string
     {
         $items = $workOrder->items;
         $lotNo = $this->generateLotNo($workOrder);
@@ -1141,6 +1148,8 @@ private function saveItemResults(WorkOrder $workOrder, ?array $resultData, int $
             $item->options = $options;
             $item->save();
         }
+
+        return $lotNo;
     }
 
     /**