A one-pack high solid coating composition consisting essentially of (I) 100 parts by weight of an acrylic resin which is a copolymer having a glass transition temperature of -21.degree. to -50.degree. C. and a hydroxyl number of 40 to 280 and being prepared from (a) one or more members selected from hydroxyalkyl acrylates and methacrylates of the general formula ##STR1## wherein R is a hydrogen atom or a methyl group and R.sub.1 is a divalent alkyl group having 2 to 5 carbon atoms, and (b) one or more members selected from alkyl acrylates and methacrylates of the general formula ##STR2## wherein R is as defined above and R.sub.2 is a monovalent alkyl group having 1 to 12 carbon atoms, and glycidyl acrylates and methacrylates of the general formula ##STR3## wherein R is as defined above and R.sub.3 is a divalent alkyl group having 1 to 5 carbon atoms, (II) 20 to 160 parts by weight of an amino-formaldehyde resin etherified with a monohydric alcohol having 1 to 4 carbon atoms, and (III) 0.5 to 6 parts by weight, per 100 parts by weight of the total of the acrylic resin as component (I) and the etherified amino-formaldehyde resin as component (II) combined, of a blocked acid catalyst, said amount of the blocked acid catalyst being expressed in the amount of its acid.