An electrodeposition coating composition comprising (a) a water-dispersible, electrically depositable binder resin and (b) water-insoluble, internally crosslinked polymer microparticles having a particle size from 0.01 to 2 microns, said polymer microparticles bearing on their surfaces physically adhered or covalently bound thereto an amphoionic group of the formula: ##STR1## wherein R represents an unsubstituted or substituted C.sub.1 -C.sub.6 alkylene or phenylene, A is --COOH or --SO.sub.3 H.