Refrigerating machine oil for hydrocarbon refrigerant and a refrigerator system using the same are provided to restrain a capillary from being stopped up or the opening and closing fail of a valve by the precipitation of wax, by lowering the precipitation temperature of wax by adding a predetermined quantity of sulfur compounds to hydrocarbon machine oil. Refrigerating machine oil used for hydrocarbon refrigerant including hydrocarbon having 1-5 carbons consists of hydrocarbon machine oil of 100wt.% and the sum of at least one of oil sulfide and olefin sulfide of 0.001-0.05wt.%. Hydrocarbon machine oil is mineral oil having %Cp over 40, a pour point below -27.5°C, and a coefficient of kinematic viscosity of 3-200mm^2/s at 40°C. The refrigerant is propane and/or isobutene.