A reciprocating piston type refrigerant compressor is disclosed which includes a compressor housing having a cylinder block provided with a plurality of cylinders and a crank chamber adjacent the cylinder block. A piston slides within each cylinder and is reciprocated by a wobble plate driven by a cam rotor. A drive shaft is connected to the cam rotor to drive the cam rotor. A front end plate is disposed on an opening of the crank chamber; the front end plate rotatably supports the drive shaft. A rear end plate is fixed on the opposite end of the compressor housing together with a valve plate which includes a suction chamber and a discharge chamber. The rear end plate is provided with a plurality of dead space chambers, each of which is connected with one of the cylinders through a hole formed through the valve plate. A valve is slidably disposed within the dead space chamber to control the opening and closing of the hole in the valve plate. The valve is controlled by a valve control device supported by the rear end plate. The valve control device is responsive to the environment to adjust the capacity of the compressor by controlling the operation of the valves.