To eliminate the fault that a crank case heater is energized after a stop time of a compressor and therefore the amount of power consumption is large, in regard to a technique of controlling the stagnation of a refrigerant in the compressor at the stop thereof.

The present air conditioner comprises an ambient temperature sensor 4, the crank case heater 8, a compressor discharge temperature sensor 9, the compressor 10, and a heat storage material 11 provided on the outer peripheral surface of the compressor 10. The energy of heating in the operation of the compressor is stored in the heat storage material. Consequently, it is made possible to reduce the lowering of the temperature of a compressor oil reservoir and to suppress the stagnation of the refrigerant.