To provide an air conditioner using a mixed refrigerant, configured to prevent reduction in performance of an evaporator due to temperature gradient and excess increase in discharge temperature during operation, while being available for cooling and heating, in a wide operating temperature range.

A double mixed refrigerant obtained by mixing R32 at a larger mixing ratio than R134a (or R1234yf) flows into a refrigerant circuit configured by connecting a compressor 12, a first heat exchanger 14, a pressure reducing means 16, and a second heat exchanger 18 by a refrigerant pipeline. In cooling operation, liquid refrigerant separated from the double mixed refrigerant branched from a position of the first heat exchanger 14 on which R134a is liquid-rich through a gas-liquid separator 22 is injected into intermediate pressure of the compressor 12. In heating operation, the circuit is switched so that the gas-liquid separator 22 is connected between the second heat exchanger 18 and the pressure reducing means 16.