Freezing cycle apparatus

In a freezing cycle apparatus that switches between a cooling mode and a heating mode, wherein a low-pressure refrigerant is evaporated in an evaporator 18 for cooling the air during a cooling mode and a hot gas refrigerant is introduced from the discharge side of a compressor 10 directly into the evaporator 18. A variable displacement type compressor capable of varying the displacement is used as the compressor 10. The displacement of the compressor 10 is controlled such that the refrigerant flow rate in the cooling or heating cycle is a predetermined target flow rate during the cooling and the heating mode.