To provide a method of manufacturing a solid electrolytic capacitor that is improved in electrical characteristics and increased in capacitance by forming a solid electrolyte layer composed of a dense and uniform conductive polymer in wound capacitor elements.

In this method, polyethylene dioxithiophene, namely, the solid electrolyte layer is also formed in the capacitor elements formed by winding anode foil and cathode foil with a separator in between, by infiltrating a mixed solution prepared by mixing 3,4-ethylene dioxithiophene and an oxidizing agent with each other at a compounding ratio of 1:3 to 1:15 into the capacitor element, and causing a polymerization reaction in the mixed solution impregnated into the separator.