 removing organic solvents having a low boiling point from the aqueous dispersion by extracting and then filtering. The cationic electrodeposition resin is prepared in the presence of an organic solvent from (a) about 00-00% by weight of a cationic electrodeposition synthetic resin produced by an epoxy-amino addition reaction (b) about 0-00% by weight of an acrylic cationic electrodeposition resin having an amino group (c) about 0-0% by weight of a fatty acid ester resin synthesized by an esterification reaction of styrene-allylalcohol copolymer and fatty acid and (d) about 00-00% by weight of polyurethane cross-linking agent produced from a mixture of blocked polymethylene polyphenyl polyisocyanate and blocked isophorone diisocyanate. The aqueous dispersion is prepared by mixing about 00-00 parts by weight of the cationic electrodeposition resin, about 00-00 parts by weight of deionized water, about 0.0-0.0 parts by weight of an acid for neutralization, about 0-0 parts by weight of a reaction product of manganese phosphate and an acid diluted in an deionized water to 00% and about 0.0-0 parts by weight of a cationic surfactant. 