The present invention proposes a lubricating oil for refrigerators comprising, as the base oil, a polyester-based derivative or a polyvinyl ether derivative and a polycarbonate-based oxygenated compound; a polyoxyalkylene glycol derivative; or a polyester-based derivative or a polyvinyl ether derivative and a polyoxyalkylene glycol derivative. The lubricating oil exhibits excellent miscibility with a refrigerant having one carbon atom and no chlorine atoms and, in particular, with difluoromethane and provides a hydraulic fluid composition exhibiting excellent antiwear, lubricity and stability.