A refrigerant circulation circuit comprises the following connected by piping: a compressor, having a low-pressure shell structure, into which a refrigerant that flows through injection piping flows; a first heat exchanger; a second heat exchanger; a first restriction device; a refrigerant-path switching device; and a second restriction device for bringing the refrigerant to an intermediate pressure when said refrigerant has passed through the first restriction device and is flowing from the second-heat-exchanger side to the first-heat-exchanger side. A control device that controls the amount of refrigerant flowing into a compression chamber from the injection piping is provided. By allowing some of the refrigerant flowing from the first-heat-exchanger side to the second-heat-exchanger side at a high pressure to be directed into the injection piping when the first heat exchanger is being used as a condenser, and by allowing some of the refrigerant that has been brought to an intermediate pressure by the second restriction device to be directed into the injection piping when the first heat exchanger is being used as an evaporator, the air-conditioning device is controlled such that the discharge temperature of the compressor does not become too high in either a heating mode or a cooling mode.
