To provide the control apparatus of the air conditioner which can defrost while carrying out heating operation, without decreasing an amount of coolant circulation by using a central path part as a condenser, and defrosting a lee side path part and a windward side path part in order by changing a rotation direction of an outdoor fan, when defrosting an outdoor heat exchanger of three-path construction.

When a detection temperature of an outside temperature sensor 10c is not less than a predetermined temperature when starting defrosting and a difference of temperature between a preset room temperature and a detection temperature of a room temperature sensor 10d is not less than a predetermined temperature, a main expansion valve 6 is fully opened; an auxiliary expansion valve 6a is throttled; a first opening/closing valve 9a and a third opening/closing valve 9c are closed; a second opening/closing valve 9b is opened; and an outdoor fan 4 is regularly rotated; a lee side path part of the outdoor heat exchanger is defrosted. When the detection temperature of a second temperature sensor 10b of the lee side path part reaches or exceeds the predetermined temperature, the outdoor fan 4 is reverse-rotated and the windward side path part of an outdoor heat exchanger is defrosted. If the detection temperature of a first temperature sensor 10a of the windward side path part reaches or exceeds the predetermined temperature, it is controled to terminate the defrosting.