An outdoor unit of an air conditioner having an expansion valve unit. The outdoor unit of the air conditioner includes a compressor, a heat exchanger configured to exchange heat between outdoor air and refrigerant compressed by the compressor, an expansion valve unit configured to decompress the refrigerant discharged from the heat exchanger, a refrigerant pipe configured to deliver the refrigerant, which is decompressed and expanded by the expansion valve unit, to the indoor unit of the air conditioner, and a bracket configured to support the expansion valve unit. The expansion valve unit includes an expansion valve, a first connection portion configured to connect the expansion valve to the heat exchanger, and a second connection portion configured to connect the expansion valve to the refrigerant pipe. The expansion valve, and one of the first connection portion or the second connection portion are fixed to the bracket.