To obtain a one-pack crosslinking coating material composition which has low effect on a base coating film, is excellent in dilutability and adhesion, and yields a coating film excellent in weather resistance, water resistance and chemical resistance.

This coating material composition comprises an unsaturated fatty acid-modified vinyl polymer solution (A) comprising an unsaturated fatty acid-modified vinyl polymer (a) having a specific structure and an organic solvent (B) containing ≥30 wt.% aliphatic hydrocarbon and a metal dryer (C). Here, the solubility parameter of mineral spirit in the unsaturated fatty acid-modified vinyl polymer solution (A) is ≥100.