The present invention relates to a solid electrolytic capacitor comprising a layer of self-doping type conductive polymer having a crosslink between polymer chains thereof on the dielectric film formed on a valve-acting metal. The present invention enables to stably produce thin capacitor elements suitable for laminated type solid electrolytic capacitors, showing less short-circuit failure and less fluctuation in the shape of element, which allows to increase the number of laminated elements in a solid electrolytic capacitor chip to make a capacitor having a high capacity, and having less fluctuation in equivalent series resistance.