There is disclosed a working fluid for refrigerating cycle equipment of refrigerant compression-type containing the refrigerant and a refrigeration lubricant for a refrigerator, wherein said refrigerant comprises a hydrocarbon having 2 to 4 carbon atoms and no halogen atom and said refrigeration lubricant comprises, as a main component, a ketone compound which is incompatible with said refrigerant. This working fluid demonstrates preferable performance even if the amount of the refrigerant is small.