To provide a production process for a thermally curable resin composition that has excellent coating layer properties including the coating layer appearance and resistance to chemicals and shows excellent storage stability by completely mixing an epoxy group-bearing vinyl copolymer with an aliphatic polycarboxylic acid and provide a coating material including the resultant thermally curable resin composition as an essential coating layer component.

The objective thermally curable resin composition is manufactured by copolymerizing (C-1) an epoxy group-bearing vinyl monomer and (C-2) other monomers copolymerizable with the monomer in the presence of an aliphatic polycarboxylic acid dissolved or dispersed in (A) a solvent. In the objective coating material, the resultant thermally curable resin composition is used as an essential coating layer component.