To achieve an highly efficient freezing operation even if an HFC-system refrigerant is used by providing a pressure-reducing device between a condenser and a connection pipe for connecting a receiver tank and controlling the pressure-reducing device so that the difference between temperatures being detected by a condensation temperature detector and a liquid refrigerant temperature detector reaches a set value.

A freezing device 1 is constituted by connecting, for example, a compressor 2, a condenser 3, a pressure-reducing device 4, a receiver tank 5, a dryer 10, a main pressure-reducing device 6, an evaporator 7, and an accumulator 8 with pipes. Then, the pressure-reducing device 4 is controlled so that the difference between a temperature being detected by a condensation temperature detector 19 and a temperature being detected by a condenser outlet refrigerant temperature detector 20 becomes a set value that is set by a temperature being detected by an evaporation temperature detector 21 and is stored in a control device 11 when a temperature being detected by the condensation temperature detector 19 is equal to or less than a first setting temperature. The setting value increases as the evaporation temperature is higher. Also, the pressure-reducing device 4 is fully opened when the temperature being detected by the condenser temperature detector 19 is equal to or more than the first setting temperature.