PURPOSE: To provide a two-stage condensation refrigerating apparatus using a non-azeotropic refrigerant, which can obtain required low temperature in conditions suppressing the decrease of coefficient of performance by using the non-azeotropic refrigerant.

CONSTITUTION: A compressor 1', cascade condenser 2', gas-liquid separator 3', cascade condenser 4', expansion mechanism 5' and evaporator 7' are connected by means of pipes in series in this order, and the separator 3' is provided with a main circuit A' for connecting a gas retaining part 31' with the condenser 4' and a compressor cooling injection circuit B' for connecting a liquid retaining part 32' of the separator 3' with the compressor 1'. These circuits are charged with a non-azeotropic refrigerant for obtaining low temperature, which contains a low boiling point refrigerant and another refrigerant having a higher boiling point than that of the former refrigerant. The condenser 2' liquefies primarily the higher boiling point refrigerant of the mixed refrigerant, and the condenser 4' condenses gas refrigerant separated by the separator 3'. Thus, a two-stage condensation refrigerating machine using the non-azeotropic refrigerant is obtained.