PURPOSE: To prevent the formation of brittle layers such as blister and cracking in paint films by adhering a reinforcing material such as surfacing mat on the recessed parts of the surface of a primer right after coating of the primer then applying top coating paint.

CONSTITUTION: The surface of a base material 1 is blasted by an ordinary method, and immediately after coating of a primer layer 2, a thin fabric-like surfacing mat 5 wherein short glass fibers of suitable sizes are distributed in random directions is placed as a reinforcing material on the primer layer 2 in the corner parts. The surface of the mat 5 is lightly pressed by using a fabric roller to impregnate the primer slightly with the mat 5, then the material is allowed to stand for a prescribed time to allow the primer layer 2 to set. Top coating paint is applied thereon form a top coating layer 3, whereby an overall paint film 4 is formed. The exfoliation of the layer 2 and the layer 3 is prevented.