PURPOSE: To perform an appropriate control of a load of a compressor, by a method wherein a driving current fed to a compressor from a frequency varying device is detected, and based on the detected results, the frequency of said device and the start and stop of the compressor are controlled.

CONSTITUTION: A driving current fed to a compressor 3 from a frequency varying device 2 is detected by a current detector 7, and based on the driving current, the frequency of the device 2 and the start and stop of the compressor 3 are controlled. When a driving current exceeds a given value or a state, in which the current exceeds the given value, continues to be kept for a given time, a frequency is reduced by the given value. In an operation at a minimum frequency at a heating operation, when a driving current exceeds the given value or a condition, in which the driving current exceeds the given value, continues to be kept for a given time, a fan 4 of an outdoor heat exchange is brought to stop running. Further, when a condition as described above occurs under a condition in which the compressor 3 runs at a minimum frequency and the fan 4 is brought to a stop, the compressor 3 is caused to stop running.