A method of manufacturing a solid electrolytic capacitor is provided for which an electrolytic polymerization solution can be used semipermanently while preventing a decrease in electrical conductivity of an electrically conductive polymer layer and an increase in ESR of the resultant electrolytic capacitor due to degradation of the electrolytic polymerization solution. The method of manufacturing a solid electrolytic capacitor as provided includes the step (A) of forming a dielectric layer on a surface of an anode element made of a valve metal, the step (B) of forming a cathode layer including an electrically conductive polymer layer on the dielectric layer, and the step (C) of adjusting the pH of a solution that contains a monomer and a dopant agent and that is used in forming the conductive polymer layer, by allowing the solution to contact an ion exchange or ion capture substance.