A compressor has a compression chamber formed in a cylinder block, a suction passage formed upstream of the compression chamber and a suction throttle valve formed in the suction passage for adjusting opening of the suction passage. The suction throttle valve has a valve hole and a valve seat formed around the valve hole, a valve body for opening and closing the valve hole and an urging member for urging the valve body in the direction which causes the valve hole to be closed. The urging member is a disk spring. The spring characteristics of the disk spring includes a range where the increasing rate of the load required for displacement of the disk spring is reduced with an increase of displacement of the disk spring. The displacement range of the valve body includes a range where the increasing rate of the load of the disk spring is reduced with an increase of the displacement of the disk spring.