The present invention is a method of forming a chipping-resistant composite paint film comprising applying an anti-chipping primer and an intermediate coating successively in the wet-on-wet method onto a electrodeposition coat baked on a substrate and baking the two wet coat in one step, wherein the anti-chipping primer comprises (a) an aqueous dispersion of an ethylene copolymer, (b) a water-based urethane resin, and (c-1) a water-miscible organic solvent having a boiling point of not lower than 80.degree. C. and of not higher than the baking temperature of the paint, or (c-2) a melamine resin.The present invention ensures improved appearance and chipping resistance of the paint film.