A plate spring is attached to the distal-end portion of a piston. The distance L1 between the distal-end portion of a plunger and a core (recessed portion) that faces the distal-end portion of the plunger is set to be shorter than the distance L2 between the distal-end portion (plate spring) of the piston and the projecting end surface of a valve main body that faces the distal-end portion of the piston with drive of a solenoid portion stopped. Consequently, when the solenoid portion is driven, the plate spring collides against the projecting end surface of the valve main body so that the plunger does not collide against the core. As a result, a shock applied to the piston can be absorbed by the elastic force of the plate spring, which suppresses generation of a sound of collision.