The present invention provides a mixed ester of: pentaerythritol or a mixed polyalcohol comprising pentaerythritol and a dipentaerythritol indicated in formula (I); and a carboxylic acid containing a 3,5,5-trimethylhexanoic acid and a 2-propylheptanoic acid. This mixed ester has a good balance of excellent characteristics, such as compatibility with a coolant containing fluoropropene, low temperature properties, oxidation stability, oxidation/hydrolytic stability, and lubrication, etc.; maintains the required viscosity range for a refrigerant oil; and can be used as an industrial lubricant for refrigerant oil, etc.