An outdoor unit of an air conditioner includes a compressor that compresses a first refrigerant introduced from an indoor unit of the air conditioner and a condenser that condenses the first refrigerant compressed by the compressor. A first driving circuit drives the compressor and a second driving circuit regulates a voltage of the first driving circuit. A cooling unit includes: a heat dissipation member that comes into thermal contact with the first driving circuit and the second driving circuit, and a refrigerant pipe that is provided in the heat dissipation member, and has a path along which a second refrigerant moves through the first driving circuit and the second driving circuit. As a result, it is possible to efficiently cool the first driving circuit and the second driving circuit.