A compressor of scroll type or the like, in which, in order to change the discharge capacity automatically in accordance with the rpm (rotational speed) of a shaft (4) by simple means, the centrifugal force exerted on a movable scroll (9) orbiting with the rotation of the shaft (4) is used as a vibratory force to forcibly vibrate a spool (23) constituting a valve body supported on an elastic member (25), thereby opening and closing bypass holes (22) for establishing communication between a working chamber (V) and a suction chamber (15).