A rust-preventive lubricating oil composition comprising a base oil; a sorbitan fatty acid ester; an overbased magnesium sulfonate; and at least one additive selected from the group consisting of a calcium sulfonate, a calcium sulfonate complex, a zinc sulfonate, a barium sulfonate, a fatty acid zinc, an oleic acid amine salt, an alkenyl succinic acid polyimide, and a benzotriazole derivative.