A reciprocating piston type compressor having a cylinder block unit closed, at at least one of the axial ends thereof, by a housing having a central suction chamber and a discharge chamber arranged around the suction chamber hermetically isolated by a separation wall integral with the housing, a valve plate interposed between the end of the cylinder block unit and the housing and having suction and discharge ports, suction passageways formed in the cylinder block unit to have fluid communication with the suction chamber via openings thereof, a plurality of pressing ribs axially integrally extending from an inner face of the housing toward the valve plate so as to apply a higher pressure to the valve plate at positions of the valve plate between respective two neighboring openings of the suction passageways in cooperation with the separating wall to prevent deformation of the valve plate due to the high pressure of the refrigerant in the respective cylinder bores whereby the hermetic seal between the valve plate and the end of the cylinder block is ensured.