Provided is a refrigerating machine oil composition, which is to be used for a refrigerant including a mixture of an unsaturated fluorinated hydrocarbon compound, a saturated fluorinated hydrocarbon compound and CO2, contains a base oil which includes at least one selected from a polyoxyalkylene glycol, a polyvinyl ether, a copolymer of a poly(oxy)alkylene glycol or a monoether thereof and a polyvinyl ether, and a polyol ester and has a kinematic viscosity at 100° C. of 2 mm2/s or more and 50 mm2/s or less and a hydroxyl value of 5 mgKOH/g or less, is able to be used for a refrigerating machine system using a refrigerant having a low global warming potential and usable especially for a car air conditioner or the like and including a mixture of an unsaturated fluorinated hydrocarbon compound, a saturated fluorinated hydrocarbon compound and CO2, and exhibits not only excellent compatibility with the refrigerant but also excellent stability.