Lubricating oil compositions comprise a lubricating base oil and (A) at least one compound selected from the group consisting of compounds represented by formula (1) below and compounds represented by formula (2) below: wherein R2, R1, R3 and R4 are each independently hydrogen or a hydrocarbon group having 1 to 30 carbon atoms, X1, X2, X3 and X4 are each independently oxygen or sulfur, but at least one of them is oxygen, and Y1 is a metal atom; and wherein R11 and R12 are each independently hydrogen or a hydrocarbon group having 1 to 30 carbon atoms, X11 and X12are each independently oxygen or sulfur, but at least one of them is oxygen, U is a monovalent metal ion, an ammonium ion or a proton, and k1 is an integer of 1 to 20. Lubricating oil compositions have excellent anti-wear properties and base number maintaining properties.