A lubricating oil for refrigerators which comprises a compound having oxygen as a base oil and is miscible with a refrigerant having no chlorine atoms and one carbon atom at a temperature of -10°C or lower when the lubricating oil is comprised at least in one content within the range of 3 to 50% by weight based on the entire amount of a mixture comprising the lubricating oil and the refrigerant; and a hydraulic fluid composition for refrigerators which comprises a refrigerant having no chlorine atoms and one carbon atom and the lubricating oil described above. The hydraulic fluid composition exhibits excellent miscibility of the lubricating oil with the above refrigerant and, in particular, with difluoromethane and also exhibits excellent antiwear, lubricity and stability.