Provided are a valve mechanism which is easy to manufacture, while suppressing inclination and eccentricity of a valve body and suppressing a deterioration in the response characteristics of the valve body, and a high-pressure fuel supply pump provided with said valve mechanism. A suction inlet valve mechanism 300 is provided with: a suction inlet valve 30 capable of being seated on and unseated from a valve seat portion 31b; and a suction inlet valve stopper 32 which regulates movement of the suction inlet valve in the valve opening direction. The suction inlet valve 30 includes: a valve main body portion 71 which is seated on the valve seat portion 31b; and a cylindrical guided portion 72 which extends toward the suction inlet valve stopper 32 side from a position on the valve main body portion 71 on the radially inner side of the valve seat portion 31b. The suction inlet valve stopper 32 includes: a stopper main body portion 81 which regulates movement of the suction inlet valve 30 in the valve opening direction by abutting a distal end portion 72c of the guided portion 72; and a cylindrical portion 82 which extends from the stopper main body portion 81 toward the valve seat portion 31b side, and which serves as a guide portion against which the guided portion 72 slides, thereby guiding the movement of the suction inlet valve 30 in the direction moving toward and away from the valve seat portion 31b.