The present invention provides a refrigerating unit comprising a high temperature side refrigerant circuit (2) and a low temperature side refrigerant circuit (3) for forming an independent refrigerant closed-circuit (3) for forming an independent closed-circuit which exhibits a refrigerating effect by that a refrigerant discharged from each compressor (4) and (10) is condensed and then is evaporated, and an evaporator (14) of the high temperature side refrigerant circuit (2) and a condenser (23) of the low temperature side refrigerant circuit (3) form a thermal exchanger (25), wherein a non-azeotropic mixture refrigerant comprising; (a) an inorganic refrigerant selected from the group consisting of argon and nitrogen, (b) a hydrocarbon which makes (a) component liquidize, and (c) at least one refrigerant selected from the group consisting of hydrochlorofluorocarbon, hydrofluorocarbon, hydrocarbon and fluorocarbon, which makes (b) component liquidize, is sealed into the low temperature side refrigerant circuit (3). Preferably, (a) component of said non-azeotropic mixture refrigerant is argon, (b) component of said non-azeotropic mixture refrigerant is methane and (c) component of said non-azeotropic mixture refrigerant is a mixture of dichlorofluoromethane, tetrafluoromethane, (d) component selected from the group consisting of chlorodifluoromethane, difluoromethane and pentafluoroethane, and (e) component which is trifluoromethane and/or hexafluoroethane.