a variable displacement type compressor in which a discharge - pressure region , a suction - pressure region and a pressure control chamber are defined , has a tiltable swash plate and a piston reciprocated by the swash plate in the pressure control chamber . the inclination angle of the swash plate and the piston stroke are changed by adjustment of pressure in the pressure control chamber thereby to control the displacement of the compressor . the compressor further comprises a supply passage for supplying refrigerant gas from the discharge - pressure region to the pressure control chamber , a release passage for releasing the refrigerant gas from the pressure control chamber to the suction - pressure region , a first control valve for adjusting a cross - sectional area of the supply passage from the discharge - pressure region to the pressure control chamber and a second control valve for adjusting cross - sectional area of the release passage . the second control valve includes a valve body for opening and closing the release passage whose cross - sectional area is set minimum when the valve body is located at the closed position and a valve spring for urging the valve body in a direction to open the release passage . when the second control valve is closed , pressure in the supply passage downstream the first control valve acts on the valve body in a direction to close the release passage and pressure in the suction - pressure region acts on the valve body in a direction to open the release passage .