Abstract: The invention provides a refrigerator oil composition comprising a base oil of a mineral oil and/or a synthetic oil, and containing (a) a partial ester of a polyalcohol and a fatty acid and (b) an acid phosphate or its amine salt; and a refrigerator oil composition comprising a base oil of a mineral oil and/or a synthetic oil, and containing any of (a) acid phosphates or their amine salts, (b) acetylene glycol alkylene oxide adducts, (c) potassium salts of fatty acids, etc., (d) organic acids, and (e) fatty acid amides. The refrigerator oil compositions have good lubricity and are especially effective for reducing the friction in both the oil region and the extreme-pressure region in the sliding area between aluminium materials and steel materials.