Disclosed is a refrigerator oil composition for use with carbon dioxide refrigerant, characterized in that the composition dissolves in an amount of at least 0.1% by mass in a supercritical carbon dioxide at a temperature of 100° C. under a pressure of 15 Mpa.The invention provides a refrigerator oil composition for carbon dioxide refrigerant which composition is employed in a refrigerating system operated in a supercritical state of carbon dioxide refrigerant and, particularly, such a composition which can enhance heat-exchange efficiency during passage of supercritical carbon dioxide through a heat exchanger as well as which has excellent durability and lubrication performance.