In the outdoor unit, the vertical compressor (3), fan unit (4), and heat exchanger (2) are arranged in one straight line.

Further, the operating efficiency of the heat exchanger (2) is enhanced, whereby the vertical compressor (3) and the motor (4a) of the fan unit (4) can be cooled with high efficiency.

An outdoor unit of an air conditioner, which comprises a vertical compressor (3) and whose housing (1) is, nonetheless, small because the components (including a heat exchanger (2)) are arranged in the housing (1) in a specific manner.