Use of a lubricant composition comprising a base oil containing a polyoxyalkylene glycol derivative as a main component in the base oil; and 1 to 20% by mass of a monoepoxy compound based on a total amount of the lubricant composition, for a refrigerator the refrigerant of which being an unsaturated fluorinated hydrocarbon compound represented by the formula alone, C p F r R s wherein R represents H; "p" represents 2 to 6, "r" represents an integer of 1 to 12, and "s" represents an integer of 0 to 11; and provided that one or more carbon-carbon unsaturated bonds are included in a molecule, wherein the polyoxyalkylene glycol derivative comprises a compound represented by a general formula: R 1 -[(OR 2) m -OR 3] n wherein R 1 represents a hydrogen atom, an alkyl group having 1 to 10 carbon atoms, an acyl group having 2 to 10 carbon atoms, or an aliphatic hydrocarbon group having 2 to 6 binding sites and 1 to 10 carbon atoms; R 2 represents an alkylene group having 2 to 4 carbon atoms; R 3 represents a hydrogen atom, an alkyl group having 1 to 10 carbon atoms, or an acyl group having 2 to 10 carbon atoms; "n" represents an integer of 1 to 6; "m" represents a number with which an average value of "m×n" becomes 6 to 80; and when a plurality of OR 2 's are present, the plurality of OR 2 's may be identical to or different from each other, and when a plurality of [(OR 2) m -OR 3]'s are present, the plurality of [(OR 2) m -OR 3]'s may be identical to or different from each other, wherein the monoepoxy compound is selected from hydrocarbyl monoglycidyl ethers having in total 6 to 16 carbon atoms, and α-olefin oxides having in total 6 to 16 carbon atoms. 1 to 20% by mass of a monoepoxy compound based on a total amount of the lubricant composition, for a refrigerator the refrigerant of which being an unsaturated fluorinated hydrocarbon compound represented by the formula alone, C p F r R s wherein R represents H; "p" represents 2 to 6, "r" represents an integer of 1 to 12, and "s" represents an integer of 0 to 11; and provided that one or more carbon-carbon unsaturated bonds are included in a molecule, wherein the polyoxyalkylene glycol derivative comprises a compound represented by a general formula: R 1 -[(OR 2) m -OR 3] n wherein R 1 represents a hydrogen atom, an alkyl group having 1 to 10 carbon atoms, an acyl group having 2 to 10 carbon atoms, or an aliphatic hydrocarbon group having 2 to 6 binding sites and 1 to 10 carbon atoms; R 2 represents an alkylene group having 2 to 4 carbon atoms; R 3 represents a hydrogen atom, an alkyl group having 1 to 10 carbon atoms, or an acyl group having 2 to 10 carbon atoms; "n" represents an integer of 1 to 6; "m" represents a number with which an average value of "m×n" becomes 6 to 80; and when a plurality of OR 2 's are present, the plurality of OR 2 's may be identical to or different from each other, and when a plurality of [(OR 2) m -OR 3]'s are present, the plurality of [(OR 2) m -OR 3]'s may be identical to or different from each other, wherein the monoepoxy compound is selected from hydrocarbyl monoglycidyl ethers having in total 6 to 16 carbon atoms, and α-olefin oxides having in total 6 to 16 carbon atoms.