A reciprocatory piston type compressor having a cylinder block in which a plurality of compression chambers permit a plurality of reciprocatory pistons to be reciprocated so as to compress a refrigerant gas drawn from a suction chamber formed in an end housing into the compression chambers through suction ports of a valve plate, opened and closed by a suction valve mechanism with a plurality of resilient radial suction valves having a free end thereof, respectively, and surrounded by cutoff slots formed in a suction valve sheet, and to discharge the compressed refrigerant gas from the compression chambers into a discharge chamber formed in the end housing through discharge ports of the valve plate, opened and closed by resilient discharge valves. Each of the cutoff slots of the suction valve sheet has a part thereof adjacent to the free end of each suction valve which is radially widened to retain a predetermined amount of the compressed gas by which the suction valves are smoothly separated from the valve plate toward the open position thereof and rest on the walls of radial recesses formed in the end of the cylinder block during the suction stroke of the compressor.