A dispersion liquid including one of thiophene and derivatives thereof, a polyanion, and a solvent is prepared. The dispersion liquid is mixed with a first oxidizing agent producing iron ions so as to oxidatively polymerize the one of thiophene and derivatives thereof. At the completion of the polymerization, the conductive polymer microparticle dispersion contains trivalent iron ions with a concentration of 3 to 30 parts by weight, inclusive, with respect to 100 parts by weight of the conductive polymer microparticle.