A lubricating oil composition prepared by blending a base oil with a polyalkylene glycol, the base oil containing a compound that is an ester or ether and has two or more aromatic rings, wherein the polyalkylene glycol has a number average molecular weight of from 2,500 to 60,000, measured by GPC as the standard polystyrene conversion, wherein the lubricating oil composition has a density at 15°C of 1.100 g/cm 3 or more, measured according to JIS K2249-1:2011, wherein the base oil contains a compound that is an ester or ether and has no aromatic ring, in addition to the compound, wherein the compound is a compound represented by the following general formula: wherein R A and R B each independently represent an alkyl group having from 1 to 30 carbon atoms, a cycloalkyl group having from 3 to 12 ring carbon atoms, an aryl group having from 6 to 12 ring carbon atoms, an alkyloxycarbonyl group having from 2 to 30 carbon atoms, or an alkylcarbonyloxy group having from 2 to 30 carbon atoms; X A and X B each independently represent a single bond, -O-, -C(=O)-, -C(=O)-O-, or -O-C(=O)-, provided that XA and XB do not simultaneously represent single bonds; Y represents an alkylene group or a (poly)oxyalkylene group; a1 and a2 each independently represent 0 or 1; p1 and p2 each independently represent an integer of from 0 to 3; and q1 and q2 each independently represent an integer of from 0 to 5, wherein the compound is a dicarboxylate ester of an ethylene glycol ether or a polyethylene glycol ether, wherein the polyalkylene glycol is a compound represented by the following general formula: R 1 -((OR 2) a -OR 3) b wherein R 1 represents a trivalent hydrocarbon group having from 1 to 10 carbon atoms; R 2 represents an alkylene group having from 2 to 4 carbon atoms; R 3 represents a hydrogen atom; b represents 3; and a represents a number of 1 or more and corresponds to the value of the number average molecular weight as defined above, provided that in the case where plural groups are present for each of R 2 and R 3, the plural groups for each of R 2 and R 3 may be the same as or different from each other, wherein a blending amount of the compound is 30% by mass or more based on the total amount of the lubricating oil composition, wherein a content ratio ( /) of the compound and the compound contained in the base oil is from 1/1 to 10/1 in terms of mass ratio, and wherein a content of the polyalkylene glycol is from 0.2 to 15% by mass based on the total amount of the lubricating oil composition. wherein the polyalkylene glycol has a number average molecular weight of from 2,500 to 60,000, measured by GPC as the standard polystyrene conversion, wherein the lubricating oil composition has a density at 15°C of 1.100 g/cm 3 or more, measured according to JIS K2249-1:2011, wherein the base oil contains a compound that is an ester or ether and has no aromatic ring, in addition to the compound, wherein the compound is a compound represented by the following general formula: wherein R A and R B each independently represent an alkyl group having from 1 to 30 carbon atoms, a cycloalkyl group having from 3 to 12 ring carbon atoms, an aryl group having from 6 to 12 ring carbon atoms, an alkyloxycarbonyl group having from 2 to 30 carbon atoms, or an alkylcarbonyloxy group having from 2 to 30 carbon atoms; X A and X B each independently represent a single bond, -O-, -C(=O)-, -C(=O)-O-, or -O-C(=O)-, provided that XA and XB do not simultaneously represent single bonds; Y represents an alkylene group or a (poly)oxyalkylene group; a1 and a2 each independently represent 0 or 1; p1 and p2 each independently represent an integer of from 0 to 3; and q1 and q2 each independently represent an integer of from 0 to 5, wherein the compound is a dicarboxylate ester of an ethylene glycol ether or a polyethylene glycol ether, wherein the polyalkylene glycol is a compound represented by the following general formula: R 1 -((OR 2) a -OR 3) b wherein R 1 represents a trivalent hydrocarbon group having from 1 to 10 carbon atoms; R 2 represents an alkylene group having from 2 to 4 carbon atoms; R 3 represents a hydrogen atom; b represents 3; and a represents a number of 1 or more and corresponds to the value of the number average molecular weight as defined above, provided that in the case where plural groups are present for each of R 2 and R 3, the plural groups for each of R 2 and R 3 may be the same as or different from each other, wherein a blending amount of the compound is 30% by mass or more based on the total amount of the lubricating oil composition, wherein a content ratio ( /) of the compound and the compound contained in the base oil is from 1/1 to 10/1 in terms of mass ratio, and wherein a content of the polyalkylene glycol is from 0.2 to 15% by mass based on the total amount of the lubricating oil composition.