A reciprocating compressor, comprising a cylinder block (1) having a cylinder bore (12) formed therein, a rear head (3) fixed to the cylinder block through a valve plate (2) and having a suction chamber (26) and a discharge chamber (27) formed therein, a front head (4) fixed to the cylinder block (1) and having a crankcase (6) formed therein, pistons (13) reciprocatingly sliding in the cylinder bore according to the rotation of a shaft (7) installed so as to pass through the crankcase (6), a means for separating lubricating oil mixed in working fluid discharged into the discharge chamber (27), and an oil tank (30) for storing the lubricating oil separated by the oil separation means, wherein the lubricating oil stored in the oil tank (30) is cooled by working fluid sucked from the outside and led into the suction chamber (26), whereby the durability of sliding portions can be increased by effectively cooling the lubricating oil in the compressor to assure excellent lubrication at the sliding portions.