To improve the seal performance and durability when a flow passage is closed by bringing an end face covered part in which an opening through which a valve head part is inserted is formed and which forms a disklike shape into surface-contact with a stepped part of the valve head part and a grip part and by fitting a cylindrical part extended from a peripheral fringe part of the end face covered part in outer periphery of the grip part.

As for a valve element 19, a flow passage 18 is closed by seating a valve head part 44 of a valve main body 40 on a valve seat part 43. The valve main body 40 is a molding made of a rubber material, and the valve head part 44 seated on the valve seat part 43 provides good adhesion property for the valve seat part 43 due to its elastic deformation. Furthermore, a grip part 45 continuos with a basic end side of the valve head part 44 is covered and reinforced with a holder 42 fitted in outer periphery thereof. Since this holder 42 is made of metal having smaller elastic deformation amount than the valve main body 40 and large mechanical strength, it prevents excessive elastic deformation of the valve main body 40 and reduces the damage of the valve main body 40 due to the repetition of opening and closing operations of the flow passage 18.