An air conditioner comprising: a compressor configured to compress and discharge a refrigerant; a condenser configured to condense the refrigerant compressed in the compressor; an expansion device configured to expand the refrigerant condensed in the condenser; an evaporator configured to evaporate the refrigerant expanded in the expansion device, to perform heat exchange between the refrigerant and indoor air, and to discharge the evaporated refrigerant to the compressor; a bypass unit configured to guide some of the refrigerant discharged from the condenser to an outlet end of the evaporator; a liquid pipe configured to interconnect the condenser and the expansion device; a bypass pipe configured to interconnect the liquid pipe and a gas pipe that interconnects the evaporator and the compressor; a control valve disposed on the bypass pipe to adjust a flow of the refrigerant; an accumulator disposed on the gas pipe to prevent liquid-phase refrigerant, among the refrigerant to be introduced into the compressor, from being introduced into the compressor; and a control unit configured to control overall operation of the air conditioner, characterized in that the air conditioner further comprises a heat exchange unit configured to perform heat exchange between some of the refrigerant discharged from the compressor and the refrigerant to be suctioned into the compressor; and an oil level sensor configured to sense a level of oil in the compressor, wherein the control unit is configured, during an oil collection operation of collecting oil remaining in the gas pipe into the compressor, to concurrently control the bypass unit so as to bypass the refrigerant, discharged from the condenser, to the outlet end of the evaporator, and the heat exchange unit so as to perform heat exchange between the refrigerant discharged from the compressor and the refrigerant to be suctioned into the compressor, wherein the heat exchange unit includes: a heat exchanger configured to perform heat exchange between some of the refrigerant discharged from the compressor and the refrigerant stored in the accumulator; and a regulation valve configured to regulate a flow of the refrigerant to be supplied to the heat exchanger, wherein the control unit is configured to execute the oil collection operation when an oil level input from the oil level sensor is lower than a reference oil level, and wherein the control unit is configured to open the control valve and the regulation valve upon the oil collection operation. a compressor configured to compress and discharge a refrigerant; a condenser configured to condense the refrigerant compressed in the compressor; an expansion device configured to expand the refrigerant condensed in the condenser; an evaporator configured to evaporate the refrigerant expanded in the expansion device, to perform heat exchange between the refrigerant and indoor air, and to discharge the evaporated refrigerant to the compressor; a bypass unit configured to guide some of the refrigerant discharged from the condenser to an outlet end of the evaporator; a liquid pipe configured to interconnect the condenser and the expansion device; a bypass pipe configured to interconnect the liquid pipe and a gas pipe that interconnects the evaporator and the compressor; a control valve disposed on the bypass pipe to adjust a flow of the refrigerant; an accumulator disposed on the gas pipe to prevent liquid-phase refrigerant, among the refrigerant to be introduced into the compressor, from being introduced into the compressor; and a control unit configured to control overall operation of the air conditioner, characterized in that the air conditioner further comprises a heat exchange unit configured to perform heat exchange between some of the refrigerant discharged from the compressor and the refrigerant to be suctioned into the compressor; and an oil level sensor configured to sense a level of oil in the compressor, wherein the control unit is configured, during an oil collection operation of collecting oil remaining in the gas pipe into the compressor, to concurrently control the bypass unit so as to bypass the refrigerant, discharged from the condenser, to the outlet end of the evaporator, and the heat exchange unit so as to perform heat exchange between the refrigerant discharged from the compressor and the refrigerant to be suctioned into the compressor, wherein the heat exchange unit includes: a heat exchanger configured to perform heat exchange between some of the refrigerant discharged from the compressor and the refrigerant stored in the accumulator; and a regulation valve configured to regulate a flow of the refrigerant to be supplied to the heat exchanger, a heat exchanger configured to perform heat exchange between some of the refrigerant discharged from the compressor and the refrigerant stored in the accumulator; and a regulation valve configured to regulate a flow of the refrigerant to be supplied to the heat exchanger, wherein the control unit is configured to execute the oil collection operation when an oil level input from the oil level sensor is lower than a reference oil level, and wherein the control unit is configured to open the control valve and the regulation valve upon the oil collection operation.