diff --git a/train_network.py b/train_network.py
index d3e34eb7..82110066 100644
--- a/train_network.py
+++ b/train_network.py
@@ -988,6 +988,7 @@ class NetworkTrainer:
                             print("Validating バリデーション処理...")
                             total_loss = 0.0
                             with torch.no_grad():
+                                validation_steps = args.validation_batches if args.validation_batches is not None else len(val_dataloader)
                                 for val_step in min(len(val_dataloader), args.validation_batches):
                                     is_train = False
                                     batch = next(cyclic_val_dataloader)
@@ -1013,6 +1014,7 @@ class NetworkTrainer:
                     print("Validating バリデーション処理...")
                     total_loss = 0.0
                     with torch.no_grad():
+                        validation_steps = args.validation_batches if args.validation_batches is not None else len(val_dataloader)
                         for val_step in min(len(val_dataloader), args.validation_batches):
                             is_train = False
                             batch = next(cyclic_val_dataloader)
@@ -1186,8 +1188,8 @@ def setup_parser() -> argparse.ArgumentParser:
     parser.add_argument(
         "--validation_batches",
         type=int,
-        default=1,
-        help="Number of val steps for counting validation loss. By default, validation one batch is performed"
+        default=None,
+        help="Number of val steps for counting validation loss. By default, validation for all val_dataset is performed"
     )            
     return parser