To obtain a working fluid which scarcely clogs a depressueizing mechanism, even when an HFC-based refrigerant is used, and to provide a freezing device.

This freezing device is characterized by charging a working fluid comprising a mixed freezer oil and an HFC-based refrigerant containing R32 in an amount of ≥50 wt.% into a freezing circuit 1. The mixed freezer oil comprises a synthetic oil such as an ether oil or an ester oil and an alkylbenzene-based oil, wherein the alkylbenzene-based oil occupies in an amount of 1 to 90 wt.% based on the mixed freezer oil.