The invention provides a thermosetting powder coating composition comprising (A) a vinyl copolymer having a number average molecular weight of 1,500 to 6,000, a molecular weight distribution of 1.0 to 1.5 as represented by a weight average molecular weight/a number average molecular weight and a glass transition temperature of 40 to 100.degree. C., the copolymer containing at least one species of functional group selected from the class consisting of epoxy group, carboxyl group and hydroxyl group, and (B) a curing agent. The thermosetting powder coating composition of the invention is superior in any of the finished appearance of coating film and the blocking resistance.