PURPOSE: To reduce pulsation sound at the refrigerant inlet time while maintaining the maximum capacity of a compressor by letting the throttle function of the protruding member of a valve body act large at the time of the lift quantity of an inlet valve body being small, and reducing the influence of the throttle function at the time of the lift quantity being large.

CONSTITUTION: When the inlet quantity of refrigerant is small, the force that is going to open an inlet valve 20 is weak, so that the lift quantity of a valve body is small, and the distance α between a fixed bush 22 and the protruding member 23a of an inner peripheral valve body 23 becomes gradually longer toward the apex of the protruding member 23a from its bottom. The throttle function thereby work larger as the lift quantity of the valve body 23 is smaller. Accordingly, the amplitude of inlet pulsation can be reduced so as to prevent the generation of pulsation sound. When the inlet quantity of the refrigerant is large, the force that is going to open the valve 20 is large, so that the lift quantity of the valve body 23 becomes large, and when the lift quantity exceeds a certain value, the valve body 23 stops displaying the function of throttling the inlet port 6a. The inlet efficiency is not therefore lowered, and the capacity of a compressor is prevented from being lowered.