diff --git a/chainercv/transforms/keypoint/flip_keypoint.py b/chainercv/transforms/keypoint/flip_keypoint.py
index 76a89befb3..d7788f2ac1 100644
--- a/chainercv/transforms/keypoint/flip_keypoint.py
+++ b/chainercv/transforms/keypoint/flip_keypoint.py
@@ -22,7 +22,7 @@ def flip_keypoint(keypoint, size, y_flip=False, x_flip=False):
     H, W = size
     keypoint = keypoint.copy()
     if y_flip:
-        keypoint[:, 0] = H - 1 - keypoint[:, 0]
+        keypoint[:, 0] = H - keypoint[:, 0]
     if x_flip:
-        keypoint[:, 1] = W - 1 - keypoint[:, 1]
+        keypoint[:, 1] = W - keypoint[:, 1]
     return keypoint
diff --git a/tests/transforms_tests/keypoint_tests/test_flip_keypoint.py b/tests/transforms_tests/keypoint_tests/test_flip_keypoint.py
index f059b47567..5dae2f8b6d 100644
--- a/tests/transforms_tests/keypoint_tests/test_flip_keypoint.py
+++ b/tests/transforms_tests/keypoint_tests/test_flip_keypoint.py
@@ -14,12 +14,12 @@ def test_flip_keypoint(self):
 
         out = flip_keypoint(keypoint, size=(34, 32), y_flip=True)
         keypoint_expected = keypoint.copy()
-        keypoint_expected[:, 0] = 33 - keypoint[:, 0]
+        keypoint_expected[:, 0] = 34 - keypoint[:, 0]
         np.testing.assert_equal(out, keypoint_expected)
 
         out = flip_keypoint(keypoint, size=(34, 32), x_flip=True)
         keypoint_expected = keypoint.copy()
-        keypoint_expected[:, 1] = 31 - keypoint[:, 1]
+        keypoint_expected[:, 1] = 32 - keypoint[:, 1]
         np.testing.assert_equal(out, keypoint_expected)