To obtain a novel coating material composition which has a low viscosity and an excellent applicability, does not stain a heating oven in curing, does not generate formalin in curing, and can form a coating film strong against acidic rain and excellent in retort resistance and adhesiveness.

This coating composition contains (A) an acrylic copolymer having hydroxy groups and (B) a half-esterification product of a copolymer (b1) prepared from styrene and maleic anhydride as essential monomers. The half-esterification product (B) is prepared by reacting acid anhydride groups of the copolymer (b1) with (b2) a monohydric alcohol.