diff --git a/khaosz/trainer/trainer.py b/khaosz/trainer/trainer.py
index 9d88704..fefa70f 100644
--- a/khaosz/trainer/trainer.py
+++ b/khaosz/trainer/trainer.py
@@ -57,22 +57,28 @@ class Trainer:
         
         try:
             self.parameter.model.train()
+            # 1.epoch
             for epoch in range(context.epoch, self.train_config.n_epoch):
                 context.epoch = epoch
                 self._call_callbacks('on_epoch_begin', context)
                 
                 for batch in context.dataloader:
                     if context.current_iter % self.train_config.accumulation_steps == 0:
+                        # 2. step
                         self._call_callbacks('on_step_begin', context)
                         self.train_config.optimizer.step()
                         self.train_config.optimizer.zero_grad()
                         self._call_callbacks('on_step_end', context)
                     
+                    # 3. batch
                     self._call_callbacks('on_batch_begin', context)
                     loss = self.train_config.strategy(batch)
                     context.loss = loss.item()
                     context.current_iter += 1
-                    loss.backward()
+                    
+                    # to make the loss normalized by accumulation steps
+                    normalized_loss = loss / self.train_config.accumulation_steps
+                    normalized_loss.backward()
                     
                     self._call_callbacks('on_batch_end', context)