Refrigerator oil and refrigerator working fluid composition

A refrigerating machine oil comprising:

• a base oil comprising an ester and comprising no ether;
• a dithiophosphoric acid ester;
• and
• a phosphonate ester;
• wherein the base oil comprises at least one selected from the group consisting of a polyol ester and a complex ester,
• the polyol ester comprises a polyol ester of pentaerythritol and a fatty acid having 4 to 9 carbon atoms,
• the complex ester is an ester synthesized from
• neopentyl glycol
• at least one selected from the group consisting of a dihydric alcohol having 2 to 10 carbon atoms other than neopentyl glycol,
• at least one selected from the group consisting of a polybasic acid having 6 to 12 carbon atoms, and
• at least one selected from the group consisting of a monohydric alcohol having 4 to 18 carbon atoms,
• a content of the base oil is 90% by mass or more based on a total amount of the refrigerating machine oil,
• the dithiophosphoric acid ester is a compound represented by the following formula (A-3):
• wherein R1 and R2 each independently represent an alkyl group having 3 or more and 9 or less carbon atoms, and R6 and R7 each independently represent a hydrogen atom or an alkyl group having 1 or more and 4 or less carbon atoms,
• a content of the dithiophosphoric acid ester is 0.01% by mass or more and 0.1% by mass or less based on a total amount of the refrigerating machine oil,
• the phosphonate ester is a compound represented by the following formula (B-2):
• wherein R11 and R12 each independently represent an alkyl group having 2 or more and 5 or less carbon atoms, R14 represents an alkylene group having 1 or more and 4 or less carbon atoms, and R15 represents a hydrogen atom, and
• a content of the phosphonate ester is 0.01% by mass or more and 0.1% by mass or less based on a total amount of the refrigerating machine oil, and wherein the refrigerating machine oil is used with a refrigerant.