A valve chamber formed between a fluid inlet and a fluid outlet in a valve casing; a valve seat having a valve hole and formed on a fluid inlet side of the valve chamber;Check Valves a valve body adapted to abut the valve seat from a fluid outlet side, the valve body being provided in the valve chamber so as to be movable in a direction in which a fluid flows, the valve body including an elastic valve body portion formed of an elastic material and an inelastic valve body portion formed of an inelastic material, Check Valvesthe inelastic valve body portion being overlapped on a fluid inlet side surface of the elastic valve body portion and having a smaller diameter than the elastic valve body portion, the valve seat including a first valve seat portion with which the elastic valve body portion abuts and a second valve seat portion with which the inelastic valve body portion abuts after the elastic valve body portion comes into abutment with the first valve seat portion, the valve body being fixed to a valve shaft while having a center thereof passed through by the valve shaft, the valve shaft having its both end portions supported by shaft support portions respectively provided on the fluid inlet and fluid outlet sides of the valve casing so as to be axially movable;CHECK VALVES a valve body abutment plate arranged on the fluid outlet side of the elastic valve body portion of the valve body and capable of abutting the elastic valve body portion, the valve body abutment plate being supported to the valve shaft so as to be axially movable relative to the valve shaft while having a center opening passed through by the valve shaft, the valve body abutment plate having: an elastic valve body portion pressing portion provided in an outer periphery of the valve body abutment plate, for pressing on an outer peripheral portion of the elastic valve body portion; and a backflow fluid pressure exerting hole for causing a fluid pressure of the fluid from the fluid outlet side to be exerted on the elastic valve body portion; and a spring for urging the valve body into abutment with the valve seat through the valve body abutment plate, the spring being interposed between the valve body abutment plate and the shaft support portion provided on the fluid outlet side.

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