A refrigerating oil composition which exhibits excellent lubrication properties when used in combination with certain types of coolant, such as a hydrofluorocarbon coolant, which may serve as substitutes for chlorofluorocarbon coolants which have been implicated as causing environmental problems. The refrigerating oil composition of the present invention is obtained by incorporating, into a component (A); i.e., a base oil containing a synthetic oil, a component (B); i.e, a polyalkylene glycol derivative of formula (I) having a number average molecular weight of 200-3,000: R1—(OR2)m—(OR3)n—OR4  (I) wherein R1 and R4 represent C1-C30 hydrocarbon groups, etc.; R2 represents a C2-C4 alkylene group; R3 represents a C2-C30 alkylene group; m and n are numbers that satisfy the above-described molecular weight conditions, wherein n may be 0; and at least one of R1, R3, and R4 has a hydrocarbon group having six or more carbon atoms.