An air conditioner, comprising: a compressor for compressing a refrigerant; a condenser for condensing the refrigerant compressed at the compressor; an evaporator for evaporating the refrigerant condensed at the condenser; and an injection module disposed between the condenser and the evaporator for separating the refrigerant flown from the condenser to the evaporator into a vapor-phase refrigerant and liquid-phase refrigerant, expanding the separated vapor-phase refrigerant and injecting the expanded refrigerant into the compressor, expanding and evaporating some of the separated liquid-phase refrigerant and injecting the expanded and evaporated refrigerant into the compressor, and supplying the remainder of the separated liquid-phase refrigerant to the evaporator, wherein the injection module comprises, an injection liquid-vapor separator, disposed between the condenser and the evaporator, for separating the refrigerant to be flown into the vapor-phase refrigerant and liquid-phase refrigerant, a first injection expansion valve, connected to the injection liquid-vapor separator and the compressor, for expanding the vapor-phase refrigerant separated from the injection liquid-vapor separator, a second injection expansion valve, connected to the injection liquid-vapor separator, for expanding some of the separated liquid-phase refrigerant, an injection heat exchanger, connected to the second injection expansion valve and the compressor and disposed at the injection liquid-vapor separator, for evaporating the refrigerant expanded at the second injection expansion valve, and a controller for controlling the air conditioner, characterized by further comprising an injection expansion temperature sensor for measuring the temperature of the refrigerant expanded at the second injection expansion valve, and an injection evaporation temperature sensor for measuring the temperature of the refrigerant evaporated at the injection heat exchanger, wherein the controller is configured to control the second injection expansion valve according to the injection superheat, that is, the difference between the temperature measured by the injection evaporation temperature sensor and the temperature measured by the injection expansion temperature sensor. a compressor for compressing a refrigerant; a condenser for condensing the refrigerant compressed at the compressor; an evaporator for evaporating the refrigerant condensed at the condenser; and an injection module disposed between the condenser and the evaporator for separating the refrigerant flown from the condenser to the evaporator into a vapor-phase refrigerant and liquid-phase refrigerant, expanding the separated vapor-phase refrigerant and injecting the expanded refrigerant into the compressor, expanding and evaporating some of the separated liquid-phase refrigerant and injecting the expanded and evaporated refrigerant into the compressor, and supplying the remainder of the separated liquid-phase refrigerant to the evaporator, wherein the injection module comprises, an injection liquid-vapor separator, disposed between the condenser and the evaporator, for separating the refrigerant to be flown into the vapor-phase refrigerant and liquid-phase refrigerant, a first injection expansion valve, connected to the injection liquid-vapor separator and the compressor, for expanding the vapor-phase refrigerant separated from the injection liquid-vapor separator, a second injection expansion valve, connected to the injection liquid-vapor separator, for expanding some of the separated liquid-phase refrigerant, an injection heat exchanger, connected to the second injection expansion valve and the compressor and disposed at the injection liquid-vapor separator, for evaporating the refrigerant expanded at the second injection expansion valve, and a controller for controlling the air conditioner, characterized by further comprising an injection expansion temperature sensor for measuring the temperature of the refrigerant expanded at the second injection expansion valve, and an injection evaporation temperature sensor for measuring the temperature of the refrigerant evaporated at the injection heat exchanger, wherein the controller is configured to control the second injection expansion valve according to the injection superheat, that is, the difference between the temperature measured by the injection evaporation temperature sensor and the temperature measured by the injection expansion temperature sensor.