Abstract: An airconditioner wherein cooling is performed by forming a refrigerant circulation passage which condenses a refrigerant delivered from a compressor by means of an outdoor heat exchanger and which evaporates it by means of an indoor heat exchanger, while warming is performed while condensing the refrigerant by means of the indoor heat exchanger by furnishing the refrigerant circulation passage with a heating heat exchanger which heats the refrigerant through a heat medium higher in temperature than the open air and which is located in parallel with the outdoor heat exchanger and between the indoor heat exchanger and the suction side of the compressor; characterized by comprising a circuit which bypasses the higher pressure side and lower pressure side of the compressor through a solenoid valve, and a controller which normally closes the bypass circuit during the cooling and normally opens the bypass circuit during the warming and which opens the bypass circuit for a predetermined period of time at the starti