In a swash plate type compressor, a rotational shaft makes a piston reciprocate through a swash plate. A suction valve plate is connected to an eccentric portion of the shaft and caused to orbit around an axis of the shaft by rotation of the shaft. Friction between the suction valve plate and a contacting end wall in which a suction port is formed naturally suppresses the rotational motion of the valve plate. Therefore, the valve plate substantially orbits about the shaft axis without rotating and opens and closes the suction port. A relative velocity between the valve plate and the end wall when the valve plate orbits without rotating is smaller than when the valve plate only rotates.