Solid electrolytic capacitor and method for producing same

Disclosed is a solid electrolytic capacitor having heat-resistance and electrical properties that are more excellent and that has a high capacitance and a low ESR. Further disclosed is a method for producing same. [1] The solid electrolytic capacitor is a thiophene derivative having a heteroatom-containing cyclic substituent group and is characterized by containing as a solid electrolyte the molecule obtained by polymerizing a compound having an alkyl substituent group on the heteroatom-containing cyclic substituent group. [2] The method for producing the solid electrolytic capacitor has a step wherein the molecule described in [1] mentioned above is formed on a valve-action metal on which a dielectric oxide film has been formed.