A check valve includes connected first and second bodies respectively disposed on upstream and downstream sides. A valve plug is disposed displaceably in a communication chamber formed in the interior of the first body. A skirt urges a main body portion of the valve plug in a direction for seating the main body portion on a valve seat surface, and is provided on the valve plug such that the main body portion is seated on the valve seat surface by an elastic force of the skirt. By supplying a pressure fluid to the first body, the valve plug is displaced in opposition to the elastic force of the skirt, whereby the interior of the first body and the interior of the second body are placed in communication and the pressure fluid is allowed to flow therethrough.