To provide a new binary refrigerating system combining an ammonia cycle and a carbon dioxide gas cycle, wherein especially an evaporator being an object is pluralized and when a cascade condenser is situated in a position lower than the position of the evaporator being an object, efficient and functional operation is effected.

The binary refrigerating system 1 is that the ammonia cycle 2 is provided with the cascade condenser 7 to cool and liquefy the carbon dioxide medium of the carbon dioxide gas cycle 3, the carbon dioxide gas cycle 3 is provided with a plurality of evaporators 14 to effect cooling of the object by evaporating a carbon dioxide medium, and it is needed to transfer the carbon dioxide medium in the carbon dioxide gas cycle 3 by a CO2 pump 9. A surge tank 11 capable of storing the carbon dioxide medium is situated between the CO2 pump 9 and the evaporator 14 being an object, and the surge tank 11 is situated in a position higher than that of the evaporator 14 being an object.