A solid electrolytic capacitor is obtained by a method comprising dissolving a polymerizable material for being converted into a conductive polymer in a water-soluble organic solvent to obtain a solution, adding the solution to water while homogenizing the solution to obtain a sol, immersing an anode body having a dielectric layer in the surface of the anode body in the sol, and applying voltage using the anode body as a positive electrode and a counter electrode as a negative electrode placed in the sol to electropolymerize the polymerizable material. An electropolymerizable liquid for producing a conductive polymer, the liquid composed of a sol comprising water, a water-soluble organic solvent, and a polymerizable material for being converted into the conductive polymer.