The present invention is a medical stopcock (1) provided with a main body (2) and a cock (3). The main body (2) is provided with a tubular part (21), an upstream port (22), a downstream port (23), and a bypass port (24). The cock (3) is provided with a cylinder part (31) and a handle (32). A groove (33) is disposed on the outer circumferential surface of the cylinder part (31). Wall parts (34a, 34b) functioning as a part of the outer circumferential surface are disposed on the interior of the groove (33).
