In a compressor shell built in an outdoor unit of an air conditioner, a compressor shell thermistor that detects a temperature of the shell is installed. Also, an outside air temperature thermistor that detects an outside air temperature is installed in an outdoor unit. The outside air temperature is compared with the compressor shell temperature, and if the shell temperature is higher than the outside air temperature, a compressor heating device is invalidated. If the shell temperature is lower than the outside air temperature, it is determined as a refrigerant collection condition, and the compressor heating device is operated. Also, if the shell temperature is higher than the outside air temperature by a certain temperature or more, the operation of the compressor heating device is stopped so that wasteful standby power is reduced, and energy of the apparatus is saved.