An air conditioner comprising: a plurality of compressors (11, 12, 13); an intake passageway configured to distribute a fluid to each of the compressors; a bypass unit including a plurality of bypass pipes (51, 52, 53) connected respectively to the compressors to discharge the fluids from the compressors to a common bypass pipe; wherein the common bypass pipe is disposed between the plurality of bypass pipes and the intake passageway; wherein the bypass pipes are provided respectively with depressurization parts (54, 55, 56) to depressurize a fluid and a plurality of temperature sensors (60, 61, 62) configured to sense temperatures of the fluids discharged from the depressurizing parts, an expansion valve disposed between the common bypass pipe and the intake passageway to control a flow rate of fluid from the common bypass pipe to the intake passageway; and a control part configured to control the operation of the expansion valve, characterized in that the control part opens the expansion valve when an open condition of the expansion valve is satisfied, the control part determines whether a temperature sensed at the temperature sensor corresponding to an operation of one of the compressors satisfies a reference oil balance temperature range when the expansion valve is opened, and if the control part determines that the temperatures sensed at the temperature sensors satisfy the reference oil balance temperature range, the expansion valve is closed in operation, and in that the temperature when the oil and refrigerant are discharged at the same time to the bypass pipes is determined as the reference oil balance temperature range. a plurality of compressors (11, 12, 13); an intake passageway configured to distribute a fluid to each of the compressors; a bypass unit including a plurality of bypass pipes (51, 52, 53) connected respectively to the compressors to discharge the fluids from the compressors to a common bypass pipe; wherein the common bypass pipe is disposed between the plurality of bypass pipes and the intake passageway; wherein the bypass pipes are provided respectively with depressurization parts (54, 55, 56) to depressurize a fluid and a plurality of temperature sensors (60, 61, 62) configured to sense temperatures of the fluids discharged from the depressurizing parts, an expansion valve disposed between the common bypass pipe and the intake passageway to control a flow rate of fluid from the common bypass pipe to the intake passageway; and a control part configured to control the operation of the expansion valve, characterized in that the control part opens the expansion valve when an open condition of the expansion valve is satisfied, the control part determines whether a temperature sensed at the temperature sensor corresponding to an operation of one of the compressors satisfies a reference oil balance temperature range when the expansion valve is opened, and if the control part determines that the temperatures sensed at the temperature sensors satisfy the reference oil balance temperature range, the expansion valve is closed in operation, and in that the temperature when the oil and refrigerant are discharged at the same time to the bypass pipes is determined as the reference oil balance temperature range.