A compression device, comprising: a reciprocating compressor which compresses gas and comprises a compression housing part (63, 66), and a heat exchanger which cools the gas compressed by the compressor, wherein the heat exchanger comprises: a body part, a cooling unit which cools gas, and a connection unit (52a, 52b, 53a) which abuts on the outside surface of the compressor and has a gas inlet passage to allow the gas discharged from a compression chamber of the compressor to flow into the cooling unit (86, 87), wherein the heat exchanger is fixed directly to the compressor, the compressor comprises another compression chamber in which the gas compressed in the compression chamber is further compressed, the connection unit (52a, 52b, 53a) further has a gas exhaust passage which exhausts gas to the other compression chamber from the cooling unit (86, 87), the heat exchanger further comprises another cooling unit which cools the gas discharged from the other compression chamber, the connection unit (52a, 52b, 53a) further has another gas inlet passage to allow gas to flow into the other cooling unit from the other compression chamber, characterized in that an outer surface of the body part vertically abuts on outside surfaces of the compression housing part (63, 66), a discharge passage opening formed in the side of the compression chamber and an opening of the gas inlet passage vertically overlap, and a suction passage opening formed in the side of the other compression chamber and an opening of the gas exhaust passage vertically overlap. a reciprocating compressor which compresses gas and comprises a compression housing part (63, 66), and a heat exchanger which cools the gas compressed by the compressor, wherein the heat exchanger comprises: a body part, a cooling unit which cools gas, and a connection unit (52a, 52b, 53a) which abuts on the outside surface of the compressor and has a gas inlet passage to allow the gas discharged from a compression chamber of the compressor to flow into the cooling unit (86, 87), wherein the heat exchanger is fixed directly to the compressor, the compressor comprises another compression chamber in which the gas compressed in the compression chamber is further compressed, the connection unit (52a, 52b, 53a) further has a gas exhaust passage which exhausts gas to the other compression chamber from the cooling unit (86, 87), the heat exchanger further comprises another cooling unit which cools the gas discharged from the other compression chamber, the connection unit (52a, 52b, 53a) further has another gas inlet passage to allow gas to flow into the other cooling unit from the other compression chamber, characterized in that an outer surface of the body part vertically abuts on outside surfaces of the compression housing part (63, 66), a discharge passage opening formed in the side of the compression chamber and an opening of the gas inlet passage vertically overlap, and a suction passage opening formed in the side of the other compression chamber and an opening of the gas exhaust passage vertically overlap. a body part, a cooling unit which cools gas, and a connection unit (52a, 52b, 53a) which abuts on the outside surface of the compressor and has a gas inlet passage to allow the gas discharged from a compression chamber of the compressor to flow into the cooling unit (86, 87), wherein the heat exchanger is fixed directly to the compressor, the compressor comprises another compression chamber in which the gas compressed in the compression chamber is further compressed, the connection unit (52a, 52b, 53a) further has a gas exhaust passage which exhausts gas to the other compression chamber from the cooling unit (86, 87), the heat exchanger further comprises another cooling unit which cools the gas discharged from the other compression chamber, the connection unit (52a, 52b, 53a) further has another gas inlet passage to allow gas to flow into the other cooling unit from the other compression chamber, characterized in that an outer surface of the body part vertically abuts on outside surfaces of the compression housing part (63, 66), a discharge passage opening formed in the side of the compression chamber and an opening of the gas inlet passage vertically overlap, and a suction passage opening formed in the side of the other compression chamber and an opening of the gas exhaust passage vertically overlap.