Provided is a solid electrolytic capacitor excellent in reliability, particularly in ESR property. In a solid electrolytic capacitor having a solid electrolyte layer, the solid electrolyte layer has a conductive polymer layer formed by a chemical polymerization method or an electrolytic polymerization method, using a polymerization liquid containing at least a monomer and a dopant-introducing agent. The dopant-introducing agent contains a dopant-introducing agent containing at least alkylammonium ions as a cationic component. The dopant-introducing agent in the polymerization liquid may further contain a dopant-introducing agent containing at least metal ions as a cationic component.