PURPOSE: To prevent blow-off of cool air upon beginning of room heating operation or finishing of defrosting operation surely by a method wherein an indoor fan is rotated after a temperature, detected by a temperature adjusting device for detecting temperature, has arrived at a temperature higher than a set value and the operation of the temperature adjusting device for detecting temperature is nullified after the beginning of the defrosting operation started by detecting frosting by a frost detector.

CONSTITUTION: When high-temperature gas is generated after a given time from starting of driving of a compressor motor 15 and the atmospheric temperature of a heat exchanger thermostat 21 has arrived at a set value, the low-temperature side contact 21b thereof is opened and the high-temperature side contact 21a is closed. Accordingly, a solenoid relay 19 is brought into nonexcited condition, the contact 14 thereof is closed and driving of the indoor fan motor 11 is initiated. When the heat exchanger, provided at the outside of a room, is frosted the frosting detector 20 is operated, the contact 20b thereof for normal heating operation time is opened and the contact 20a is closed. According to these operations, exciting of a four-way valve 18 is released to switch a room heating circuit into a defrosting circuit (a cooling circuit). When the contact 20a is closed, the solenoid relay 19 is excited and the contact thereof is opened, therefore, the indoor fan motor 11 is not driven.