To prevent hunting of a valve member in a check valve.

A valve member constituted of a valve part 43 and a piston part 44, is reciprocatably stored in a piston storage cylinder part 414 of a case 41, a damper chamber 418 being a substantially sealed space is formed on an anti-valve seat side in the valve members 43 and 44, and fluid flows without passing through the damper chamber 418. According to this, since the fluid does not pass through the damper chamber 418, fluid force generated in the piston part 44 by a fluid flow is hardly varied, and the hunting of the valve members 43 and 44 is hardly increased. For a vibration component in the reciprocating direction of the valve members 43 and 44, the amplitude can be reduced by damping force generated by the damper chamber 418.