A reciprocating compressor comprises: a cylinder having an oil pocket on an inner circumferential surface of a piston insertion hole for inserting a piston with a predetermined width and depth; and a piston having a bearing portion protruding so as to slidably contact an inner circumferential surface of the piston insertion hole, and inserted into the piston insertion hole of the cylinder, wherein the bearing portion is formed to have a length shorter than that of the oil pocket of the cylinder. Accordingly, a frictional loss between the cylinder and the piston is reduced.