To provide a structure of a check valve capable of resolving the defective operation of a valve element without opening a lid of a valve casing.

This ball check valve 100 comprises the ball-shaped valve element 107 movably mounted in a flow channel from a primary side 101a of the valve casing 101 toward a secondary side 101b, and a valve seat 106 for seating the valve element 107 at the primary side of the flow channel. A valve element moving means 110 for forcibly moving the valve element 107 seated on the valve seat 106 to the secondary side is mounted in a state of being faced to the inside of the valve casing 101. Whereby the defective operation of the valve element 107 can be resolved without opening the valve lid 103.