PURPOSE: To provide a refrigerator oil which is used in a refrigerator using ammonia as the refrigerant and is excellent in the compatibility with ammonia as well as in lubricity and the stability in an ammoniac atmosphere by using a specific polyether compd. as the main component.

CONSTITUTION: At least one polyether compd. selected from the group consisting of compds. of formulas I to V (wherein R and R1 to R10 are each independently 1-8C alkyl; the number of carbon atoms per molecule excluding those in oxypropylene and oxyethylene groups is 10 or lower; and each of m1 to m10 and n1 to n10 is such an integer that the average mol.wt. of each compd. is 300-1800 provided that each of n1 to n10 is 0 or an integer not higher than the corresponding m1 to m10, which may be a random copolymer or a block copolymer, is used as the main component of a refrigerator oil. If necessary, a load- bearing additive, an antioxidant, a metal deactivator, an antifoaming agent, an oiliness improver, an anticorrosive agent, etc., are added to the oil.