PURPOSE: To reduce the cost of the title device by connecting a single-phase 200-V inverter circuit between each phase of a three-phase four-wire 400-V power source and the neutral connected to the neutral point of each phase.

CONSTITUTION: Single-phase 200-V voltages are respectively applied across input terminals A and N of the first to third inverter circuit 13a-13c and three- phase electric power of a prescribed operating frequency is supplied to the first to third compressors 3a-3c from the circuits 13a-13c so as to operate the compressors 3a-3c simultaneously like one compressor. As a result, a high- temperature high-pressure gaseous coolant is discharged to a discharged-side header from the discharge openings of the compressors 3a-3c and the coolant circulates through a refrigeration cycle at the time of refrigerating operation following the switching operation of a four-way valve. In other words, the high-temperature high-pressure gaseous coolant flows through an outside heat exchanger where the coolant is cooled and condensed to a liquid coolant as the heat is radiated from the coolant.