diff --git a/optim_nn_core.py b/optim_nn_core.py
index f2b8b2f..e2be96d 100644
--- a/optim_nn_core.py
+++ b/optim_nn_core.py
@@ -393,6 +393,20 @@ class Reshape(Layer):
         assert dY.shape[0] == self.batch_size
         return dY.reshape(self.batch_size, *self.input_shape)
 
+class Flatten(Layer):
+    def make_shape(self, shape):
+        super().make_shape(shape)
+        self.output_shape = (np.prod(shape),)
+        return shape
+
+    def F(self, X):
+        self.batch_size = X.shape[0]
+        return X.reshape(self.batch_size, *self.output_shape)
+
+    def dF(self, dY):
+        assert dY.shape[0] == self.batch_size
+        return dY.reshape(self.batch_size, *self.input_shape)
+
 class Affine(Layer):
     def __init__(self, a=1, b=0):
         super().__init__()