To enable continuous heating and defrosting by using a plurality of compressors and prevent heating efficiency from decreasing during the continuous heating and defrosting due to piping resistance and the like on an indoor heat exchanger side resulting from an increase in the number of stories of a building and the like.

A refrigeration cycle wherein cooling and heating are switched by switching a four-way valve 4 is provided with a plurality of compressors 2a and 2b. This refrigeration cycle separately forms during defrosting a defrosting circuit for introducing a discharged refrigerant of one compressor 2a to an outdoor heat exchanger 7 by means of a first defrosting bypass circuit 21 and a heating circuit for introducing a discharged refrigerant of the other compressor 2b into an indoor heat exchanger 5 to be returned by a second defrosting bypass circuit 22. According to this arrangement, defrosting and heating are performed and a heating effect is improved independently of the intensity of piping resistance of the indoor heat exchanger 5 side due to an increase in the number of stories of a building and the like.