An outdoor unit of an air conditioner having an improved structure to efficiently cool a heating unit of electronic parts therein, a cooling unit applied to the outdoor unit, and a method for manufacturing the cooling unit are provided. The outdoor unit of an air conditioner includes a case, a compressor for compressing a refrigerant, a condenser for condensing a refrigerant discharged from the compressor, electronic parts arranged in the case; and a cooling unit arranged to cool the electronic parts, wherein the cooling unit comprises a heat radiation member arranged to receive and cool down heat produced from the electronic parts, and to come into contact with at least a part of a cooling pipe in which the refrigerant flows, and a plurality of heat transfer fins formed at least some part of the heat radiation member.