PURPOSE: To restrict an increased variation of driving load and an increased variation of temperature in an intermittent injection type freezing cycle having two compressors.

CONSTITUTION: A first compressor 1a, a condensor 2, a first pressure reducing device 3, a gas-liquid separator 4, a second pressure reducing device 5 and an evaporator 6 are connected in series. A gaseous refrigerant side of the gas- liquid separator 4 and a suction side of the first compressor 1a are connected by a bypass circuit 7. There is provided a second compressor 1b of which discharging side is merged with the first compressor 1a and its suction side is branched from a downstream side of the evaporator 6 and connected while bypassing the bypass circuit 7. Between the condensor 2 and the first pressure reducing device 3 is arranged a first solenoid valve 11. The bypass circuit 7 is provided with a second solenoid valve 12. The first solenoid 11 and the second solenoid valve 12 are cooperatively controlled for their opening or closing in response to a liquid surface of the gas-liquid separator 4, thereby the second compressor 1b is separated from the intermittent injection operation.