Refrigerator oil, and working fluid composition

A working fluid composition comprising:

• a refrigerating machine oil;
• and
• a refrigerant;
• wherein
• the refrigerating machine oil comprises
• an ester of a polyhydric alcohol and a fatty acid having 14 to 20 carbon atoms, as a base oil, and
• a phosphorus-based anti-wear agent;
• the fatty acid having 14 to 20 carbon atoms comprises an unsaturated fatty acid;
• the unsaturated fatty acid comprises an unsaturated fatty acid having one carbon-carbon unsaturated bond and an unsaturated fatty acid having two or more carbon-carbon unsaturated bonds;
• a proportion of the unsaturated fatty acid having two or more carbon-carbon unsaturated bonds is 1% by mole or more and 20% by mole or less based on a total amount of the unsaturated fatty acid;
• a content of the phosphorus-based anti-wear agent is 0.1% by mass or more;
• and
• the refrigerant comprises a hydrocarbon.