A lubricant base oil composed of an ester. The ester includes a component (A) derived from trimethylolpropane in a molar percentage Amol % of 25 to 42 mol %; components (B) derived from monovalent straight-chain saturated fatty acids each having a carbon number of 8 to 12 in a molar percentage Bmol % of 33 to 55 mol %: and a component (C) derived from adipic acid in a molar ratio Cmol % of 12 to 34 mol %. The components (B) include lauric acid in a molar percentage of 5 to 50 mol %, and (BCOOH+CCOOH)/AOH is 0.90 to 1.02. AOH represents a hydroxyl equivalent of the component (A), BCOOH represents a carboxyl group equivalent of the components (B); and CCOOH represents a carboxyl group equivalent of the component (C).