A compressor comprises a plurality of pairs of a cylinder bore and a piston moving reciprocally in the cylinder bore, a valve plate provided with a plurality of outlet holes for leading pressurized gas in the cylinder bores to the outside, a plurality of strap-shaped outlet valves, each whereof is free at one longitudinal end opposing a corresponding one of the outlet holes to open and close it, and a plurality of retainers, each whereof extends in the same direction as a corresponding one of the outlet valves and is provided with a divergence restricting surface opposing the valve plate with the corresponding outlet valve extending between the surface and the valve plate to restrict the divergence of the corresponding outlet valve. The divergences of the outlet valves restricted by the retainers are different from each other.