To provide a check valve for mitigating an ill effect of water hammer.

In the check valve 100, when the inflow of fluid is stopped, a valve energizing mechanism 140 energizes an inflow shutoff valve 120 to immediately shut off an inflow port 111. When the flow of the fluid is immediately interrupted in this way, water hammer occurs but a resistance energizing mechanism energizes a flow resistive element 150 to resiliently resist the water hammer. Thus, the ill effect of the water hammer is mitigated.