To enhance efficiency of cooling operation by causing a liquid phase refrigerant to flow into an indoor heat exchanger so as to increase quantity of heat exchange in the cooling operation.

An air conditioner has a gas-liquid separator 9 provided between an expansion valve 4 constituting a refrigerant circuit and the indoor heat exchanger 5, and is further provided with a bypass pipe 10 having a check valve 11 connected to a connection port 9c for discharging a gas phase refrigerant on the gas-liquid separator 9 and a pipe 8 connecting a four-way valve 2 and the indoor heat exchanger 5. In the cooling operation, the refrigerant is separated into the gas phase refrigerant and the liquid phase refrigerant by the separator 9 so as to allow the liquid phase refrigerant to flow into the indoor heat exchanger 5.