A lubricating oil composition comprising: 100 mass parts of an ester compound described below; 0.05 to 1.5 mass parts of an amine salt of an acidic phosphoric ester described below; and 0.01 to 0.50 mass parts of a monoesterified compound described below. said ester compound of trimethylolpropane, a straight-chain saturated fatty acid having a carbon number of 8 to 10 and adipic acid, said ester compound satisfying the relationship of TMP mol%: FA mol%: AD mol% of 20 to 40 %: 40 to 70 %: 5 to 25 %, respectively, provided that TMP mol% is assigned to the molar percentage of the component derived from trimethylolpropane, FA mol% is assigned to the molar percentage of the component derived from said straight-chain saturated fatty acid having a carbon number of 8 to 10, and AD mol% is assigned to the molar percentage of adipic acid said amine salt of said acidic phosphoric ester represented by the following formula n represents an integer of 1 or 2, R' represents an alkyl group having a carbon number of 4 to 6, and R" represents hydrogen atom or an alkyl group having a carbon number of 11 to 14. said monoesterified compound of an alkane diol having a carbon number of 3 to 8 and of succinic acid having an alkyl group having a carbon number of 8 to 18 or an alkenyl group having a carbon number of 8 to 18. 100 mass parts of an ester compound described below; 0.05 to 1.5 mass parts of an amine salt of an acidic phosphoric ester described below; and 0.01 to 0.50 mass parts of a monoesterified compound described below. said ester compound of trimethylolpropane, a straight-chain saturated fatty acid having a carbon number of 8 to 10 and adipic acid, said ester compound satisfying the relationship of TMP mol%: FA mol%: AD mol% of 20 to 40 %: 40 to 70 %: 5 to 25 %, respectively, provided that TMP mol% is assigned to the molar percentage of the component derived from trimethylolpropane, FA mol% is assigned to the molar percentage of the component derived from said straight-chain saturated fatty acid having a carbon number of 8 to 10, and AD mol% is assigned to the molar percentage of adipic acid said amine salt of said acidic phosphoric ester represented by the following formula n represents an integer of 1 or 2, R' represents an alkyl group having a carbon number of 4 to 6, and R" represents hydrogen atom or an alkyl group having a carbon number of 11 to 14. said monoesterified compound of an alkane diol having a carbon number of 3 to 8 and of succinic acid having an alkyl group having a carbon number of 8 to 18 or an alkenyl group having a carbon number of 8 to 18. said ester compound of trimethylolpropane, a straight-chain saturated fatty acid having a carbon number of 8 to 10 and adipic acid, said ester compound satisfying the relationship of TMP mol%: FA mol%: AD mol% of 20 to 40 %: 40 to 70 %: 5 to 25 %, respectively, provided that TMP mol% is assigned to the molar percentage of the component derived from trimethylolpropane, FA mol% is assigned to the molar percentage of the component derived from said straight-chain saturated fatty acid having a carbon number of 8 to 10, and AD mol% is assigned to the molar percentage of adipic acid said amine salt of said acidic phosphoric ester represented by the following formula n represents an integer of 1 or 2, R' represents an alkyl group having a carbon number of 4 to 6, and R" represents hydrogen atom or an alkyl group having a carbon number of 11 to 14. n represents an integer of 1 or 2, R' represents an alkyl group having a carbon number of 4 to 6, and R" represents hydrogen atom or an alkyl group having a carbon number of 11 to 14. said monoesterified compound of an alkane diol having a carbon number of 3 to 8 and of succinic acid having an alkyl group having a carbon number of 8 to 18 or an alkenyl group having a carbon number of 8 to 18.