To provide a high-solid coating composition capable of forming a coated film excellent in weather resistance, scratch resistance and acid resistance, and having a high styrene concentration, and further to provide a method for coating the composition, and an article coated thereby.

This thermoset coating composition is characterized in that the composition contains (A) a hydroxy-containing copolymer solution containing a copolymer obtained by carrying out a radical polymerization reaction of monomers consisting of 35-70 wt.% styrene, 10-40 wt.% hydroxy-containing radically polymerizable unsaturated monomer, and 10-55 wt.% other radically polymerizable monomers as monomer components constituting the copolymer, by using a polymerization initiator of a dialkyl peroxide having 5-7C alkyl groups at both molecular terminals respectively in an organic solvent, and having 1,000-5,000 number average molecular weight and a molecular weight distribution having 1.5-3.0 ratio of Mw/Mn, (B) a curing agent having reactivity with the hydroxy group, and optionally (C) polymer fine particles containing 35-70 wt.% styrene as a monomer component constituting the polymer fine particles. The coating method and a coated article are also included.