PURPOSE: A method for forming a coat is provided, to inhibit the mixing of a middle coat and a base coat, to prevent the thickening of color and to improve the appearance of a coat. CONSTITUTION: The method comprises the steps of coating a middle paint on an electrodeposition coat formed on a substrate; coating a base paint; a coating a transparent paint; and sintering and curing the coated three layers simultaneously, wherein the middle paint comprises 40-56 wt% of a urethane-modified polyester resin having a number average molecular weight of 1,500-3,000 and obtained by reacting a polyester resin having a hydroxyl group with a glass transition temperature of 40-80 deg.C and an aliphatic isocyanate compound; 10-30 wt% of a melamine resin; 15-30 wt% of an isocyanate compound blocked with a compound having an active methylene group, obtained by the reaction of hexamethylene diisocyanate and a compound capable of reacting the hexamethylene diisocyanate; 4-15 wt% of a nonaqueous dispersion resin having a core-shell structure; and 0.4-2 parts by weight of a flake-type pigment having a long diameter of 1-10 micrometers and a number average diameter of 2-7 micrometers based on 100 parts by weight of the resin solid part. The shell part comprises an acryl resin which is obtained by copolymerization of an α,β-ethylenically unsaturated monomer mixture having a solubility parameter (SP) of 8.5-12.0 and has a number average molecular weight of 1,000-20,000; the core part comprises an acryl resin which is obtained by copolymerization of an α,β-ethylenically unsaturated monomer mixture having a solubility parameter of 12.0-16.0 and has a number average molecular weight of 15,000-50,000; and the difference of the SP of the monomer mixture of a shell part and that of the monomer mixture of a core part is 1.0-5.0.
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