diff --git a/app/Modules/Production/Controllers/ProductionOrderController.php b/app/Modules/Production/Controllers/ProductionOrderController.php
index 8a5e571..dca13f8 100644
--- a/app/Modules/Production/Controllers/ProductionOrderController.php
+++ b/app/Modules/Production/Controllers/ProductionOrderController.php
@@ -436,6 +436,21 @@ class ProductionOrderController extends Controller
                     throw new \Exception('必須提供成品批號');
                 }
 
+                // --- 新增：計算原物料投入總成本 ---
+                $totalCost = 0;
+                $items = $productionOrder->items()->with('inventory')->get();
+                foreach ($items as $item) {
+                    if ($item->inventory) {
+                        $totalCost += ($item->quantity_used * ($item->inventory->unit_cost ?? 0));
+                    }
+                }
+                
+                // 計算單位成本 (若產出數量為 0 則設為 0 避免除以零錯誤)
+                $unitCost = $productionOrder->output_quantity > 0 
+                    ? $totalCost / $productionOrder->output_quantity 
+                    : 0;
+                // --------------------------------
+
                 // 更新單據資訊：批號、效期與自動記錄生產日期
                 $productionOrder->output_batch_number = $batchNumber;
                 $productionOrder->expiry_date = $expiryDate;
@@ -446,6 +461,7 @@ class ProductionOrderController extends Controller
                     'warehouse_id' => $warehouseId,
                     'product_id' => $productionOrder->product_id,
                     'quantity' => $productionOrder->output_quantity,
+                    'unit_cost' => $unitCost, // 傳入計算後的單位成本
                     'batch_number' => $batchNumber,
                     'box_number' => $productionOrder->output_box_count,
                     'arrival_date' => now()->toDateString(),