PURPOSE: To improve operation efficiency, ensuring smooth cooling of operation even with lower fresh air by driving an outdoor fan with an inverter to finally adjusting the amount of air from the outdoor fan, and controlling the number of revolutions of the outdoor fan on the basis of high pressure side pressure and the degree of overheating.

CONSTITUTION: In cooling operation of an air conditioner, once high pressure side pressure HP detected by a high pressure sensor HP reaches a predetermined value or lower, air flow control means 51 controls an inverter 10 such that the number of revolutions of an outdoor fan 2a is reduced. Hereby, the condensation amount of a refrigerant in an outdoor heat exchanger 2 is reduced while high pressure side pressure HP is raised to keep its level at a predetermined value or higher. On the other hand, once the degree Sh of overheating of the refrigerant detected by degree-of-overheating detector means 50 reaches a proper range or higher, the air flow control mean 51 controls the inverter 10 so as to increase the number of revolutions of the outdoor fan 2a. Thus, the amount of condensation of the refrigerant is increased and the amount of evaporation of the refrigerant in an indoor heat exchanger 5 as an evaporator is increased, so that the degree Sh of overheating is lowered and kept within a proper range.