A compressor has a cylinder block (12) and rear housing (13) fixed to the cylinder block. The cylinder block has a plurality of cylinder bores (17) arranged along a first phantom circle about an axis (L) of a drive shaft (16) supported by the cylinder block. Each of the cylinder bore has a piston (18) movably disposed therein. A partition (33) is formed within the rear housing to define a discharge chamber (21) and a suction chamber (22) in the rear housing. A valve plate (14) is interposed between the chambers and the cylinder bores to selectively connect and disconnect the chambers with the cylinder bores. A separator (34) is located between an end of the partition and the valve plate to urge the valve plate against the cylinder block on a second phantom circle about the axis of the drive shaft in such a manner as to maintain selectively connecting and disconnecting the chambers with the cylinder bores.