An outdoor unit for an air conditioner is provided. The outdoor unit includes a base disposed on lower portions of suction panels, the base having two long sides and two short sides, legs respectively disposed on lower portions of the two long sides of the base, a compressor and an outdoor heat exchanger disposed on an upper portion of the base, a refrigerant tube connecting the compressor and the outdoor heat exchanger to each other, a plurality of service valve assemblies connected to the refrigerant tube, and a plurality of connection tubes respectively connected to the plurality of service valve assemblies to extend downward from the base. The plurality of connection tubes are aligned at a first alignment position at which they extend toward the front of the base or a second alignment position at which they extend toward a side of the base.