diff --git a/common/functions.py b/common/functions.py
index a1d4f712..514def2b 100644
--- a/common/functions.py
+++ b/common/functions.py
@@ -53,7 +53,7 @@ def cross_entropy_error(y, t):
         t = t.argmax(axis=1)
              
     batch_size = y.shape[0]
-    return -np.sum(np.log(y[np.arange(batch_size), t])) / batch_size
+    return -np.sum(np.log(y[np.arange(batch_size), t] + 1e-7)) / batch_size
 
 
 def softmax_loss(X, t):