An outdoor unit of an air conditioner includes a compressor-driving inverter circuit to convert direct current power for driving a compressor into pseudo three-phase alternating current power using a plurality of switching elements; a fan rotational speed detection unit to detect the fan rotational speed of a fan that cools the switching elements; an ambient temperature detection unit to detect the ambient temperature at a location where the air conditioner is located; and a compressor inverter drive unit to control the compressor rotational speed of the compressor by controlling the compressor-driving inverter circuit. The compressor inverter drive unit controls the compressor-driving inverter circuit on the basis of the fan rotational speed and the ambient temperature.