PURPOSE: To prevent suction of liquid refrigerant to a compressor at the time of heating and to suppress a decrease in cooling performance at the time of cooling by disposing an accumulator on the way of a tube for connecting a four-way valve for switching a flow of refrigerant between a flow at the time of cooling and a flow at the time of heating to an outdoor side heat exchanger.

CONSTITUTION: An accumulator 8 is disposed on the way of a tube for connecting a four-way valve 2 for switching a flow of refrigerant between a flow at the time of cooling and a flow at the time of heating to an outdoor heat exchanger 3. Gas refrigerant of high pressure and high temperature discharged from a compressor 1 is liquefied through the valve 2 and an indoor heat exchanger 7, and stored in a liquid receiver 5 through an opened check valve 4b. Liquid refrigerant of high pressure from the receiver 5 is reduced under pressure by an expansion valve 6n, vaporized through the exchanger 3, and fed to the accunaulator 8. The vapor and the liquid are separated in the accumulator 8, the liquid refrigerant is stopped in the accumulator 8, and only the gas refrigerant is circulated to the compressor 1 through the valve 2.