PURPOSE: To facilitate the control of a cooling fan by guiding a detecting value from an outside air temperature sensor to a controlling microcomputer, comparing it with a prescribed set value preset to the controlling microcomputer, breaking a delay timer function when the detecting value exceeds the get value and driving the cooling fan.

CONSTITUTION: A controlling microcomputer 5 fetches a detecting value from an outside air temperature sensor 7 upon start of a compressor 1, converts it by an A/D converter 8 and compares the converted value with respective set values preset to the controlling microcomputer 5. When the set value exceeds the detecting value form the outside air temperature sensor 7, a delay timer 9 is cancelled and a cooling fan is driven synchronizing with starting of the compressor 1. When the set value is lower than the detecting value, the cooling fan 3 is not driven. Accordingly, the compressor 1 can be easily and effciently cooled based on an outside temperature and a wasteful power consumption can be suppressed.