PURPOSE: To avoid the irregular open and close motion of a valve plate for maintaining the predetermined opening thereof, and prevent the occurrence of a noise or a vibration, even upon the occurrence of the variation of flow state in upstream piping, by providing such an opening adjustment mechanism as corresponding at least to one of a plurality of valve plates.

CONSTITUTION: In a swing check valve with a plurality of valve plates, two valve plates 1A and 1B are fixed to valve stems 3A and 3B journalled to both support sections of a valve box 2 in such state as freely rotatable and liquidtight or airtight. Also, the valve seat sections 5 of the plates 1A and 1B contact and part from valve box seat sections 4 for open and close operation, as a result of turning motion in an open direction due to a forward flow fluid P1 in the valve box 2, and turning motion in a close direction due to a reverse flow fluid P2 and own weight. In addition, a valve opening adjustment mechanism 7 is provided, so as to correspond to one valve plate 1A of the two. According to this construction, when the protrusion amount of the adjusting screw B of the mechanism 7 into the valve box 2 is made large and the opening of the valve plate 1A is restricted to be small, the irregular open and close motion of the other valve plate 1B can be avoided and the opening thereof can be maintained at the preset level, even upon the occurrence of the variation of a flow in upper stream piping 6.