To surely obtain a specified liquid super-cooling degree by a method wherein a by-pass circuit is provided on a refrigerant liquid piping, and a liquid refrigerating apparatus which refrigerates a refrigerant liquid by vacuumizing one part of the refrigerant liquid of a high pressure, of the total refrigerant circulation amount, and evaporating it, with the evaporation latent heat, is provided for the refrigerating of the refrigerant liquid.

This liquid refrigerating apparatus also works as a receiver tank 4, and a refrigerant liquid stays inside. Also, at a lower part in the liquid refrigerating apparatus 3, a refrigerating pipe 7 is provided, and normally, the refrigerating pipe 7 is immersed in the refrigerant liquid. When a compressor suction gas of a low temperature passes through the refrigerating pipe 7, the gas heat-exchanges with the liquid staying in the liquid refrigerating apparatus 3, and the liquid is super-cooled. By this method, the specified super-cooling degree of the refrigerant liquid can be stabilized, and a flush gas in the liquid piping can be prevented from generating, and a stable operation state can be obtained.