PURPOSE: To simplify the constitution of an entire system and prevent the generation of fluctuations in the differential pressure between an inlet side and an outlet side of an expansion turbine in a refrigeration cycle.

CONSTITUTION: A turbine inlet side flow passage 39 of a refrigeration cycle E is connected to a high pressure line which passes through heat exchangers 23, 24 and 26 in a circulation cycle D while a turbine outlet side flow passage 40 is connected to a low pressure line 31 which passes through a low pressure side flow passage of the heat exchangers 23, 24 and 26 respectively. Furthermore, a journal inlet side flow passage 43 of a turbine journal line F is connected to a flow passage 32 on the outlet side of a compressor in the circulation cycle D while a journal outlet side flow passage 44 is connected to a flow passage on the inlet side of the compressor respectively, thereby sharing the compressor 21 for the circulation cycle D and the refrigerating cycle E in the combination form.