An air conditioner comprising: a refrigerant circuit configured by connecting, via a liquid refrigerant communication pipe and a gas refrigerant communication pipe, an outdoor unit having a compressor and an outdoor heat exchanger, and a plurality of indoor units (5a, 5b) each having an indoor expansion valve (51a, 51b) and an indoor heat exchanger (52a, 52b), with a refrigerant filled into the refrigerant circuit being circulated through in the sequence of the compressor, the outdoor heat exchanger, the liquid refrigerant communication pipe, the indoor expansion valve, the indoor heat exchanger, the gas refrigerant communication pipe, and the compressor, wherein an outdoor liquid refrigerant pipe connecting a liquid-side end of the outdoor heat exchanger and the liquid refrigerant communication pipe is connected to a refrigerant returning pipe that branches off a portion of the refrigerant flowing through the outdoor liquid refrigerant pipe and returns the portion of the refrigerant to the compressor, and the outdoor liquid refrigerant pipe is provided with a refrigerant cooler configured to cool the refrigerant flowing through the outdoor liquid refrigerant pipe using the refrigerant flowing through the refrigerant returning pipe, and wherein a liquid pressure adjusting expansion valve configured to reduce a pressure of the refrigerant is located in the outdoor liquid refrigerant pipe at a part thereof between the liquid refrigerant communication pipe and the refrigerant cooler so that the refrigerant flows through the liquid refrigerant communication pipe in a gas-liquid two-phase state and so that the refrigerant flows through an outlet of the refrigerant cooler in a liquid state, wherein the outdoor unit and/or the plurality of indoor units (5a, 5b) have a control unit that is configured to control constituent components of the air conditioner including the liquid pressure adjusting expansion valve, characterized in that the control unit is configured to use the liquid pressure adjusting expansion valve to reduce the pressure of the refrigerant so that the refrigerant flows through the liquid refrigerant communication pipe in the gas-liquid two-phase state and so that the refrigerant flows through the outlet of the refrigerant cooler in the liquid state, by controlling an opening degree of the liquid pressure adjusting expansion valve such that a subcooling degree of the refrigerant at the liquid-side end of the outdoor heat exchanger reaches a target subcooling degree. wherein an outdoor liquid refrigerant pipe connecting a liquid-side end of the outdoor heat exchanger and the liquid refrigerant communication pipe is connected to a refrigerant returning pipe that branches off a portion of the refrigerant flowing through the outdoor liquid refrigerant pipe and returns the portion of the refrigerant to the compressor, and the outdoor liquid refrigerant pipe is provided with a refrigerant cooler configured to cool the refrigerant flowing through the outdoor liquid refrigerant pipe using the refrigerant flowing through the refrigerant returning pipe, and wherein a liquid pressure adjusting expansion valve configured to reduce a pressure of the refrigerant is located in the outdoor liquid refrigerant pipe at a part thereof between the liquid refrigerant communication pipe and the refrigerant cooler so that the refrigerant flows through the liquid refrigerant communication pipe in a gas-liquid two-phase state and so that the refrigerant flows through an outlet of the refrigerant cooler in a liquid state, wherein the outdoor unit and/or the plurality of indoor units (5a, 5b) have a control unit that is configured to control constituent components of the air conditioner including the liquid pressure adjusting expansion valve, characterized in that the control unit is configured to use the liquid pressure adjusting expansion valve to reduce the pressure of the refrigerant so that the refrigerant flows through the liquid refrigerant communication pipe in the gas-liquid two-phase state and so that the refrigerant flows through the outlet of the refrigerant cooler in the liquid state, by controlling an opening degree of the liquid pressure adjusting expansion valve such that a subcooling degree of the refrigerant at the liquid-side end of the outdoor heat exchanger reaches a target subcooling degree.