There is a solid electrolytic capacitor having a low ESR characteristic. In accordance with the solid electrolytic capacitor using an capacitor element wherein solid electrolyte is formed, the post-etching void factor of the anode foil used for the capacitor element is set at not more than 51% or the post-etching void factor of the cathode foil used for the capacitor element is set at not more than 44%, so that an electrode foil increases in conductivity and decreases in resistivity, to thereby obtain, coupled with the solid electrolyte of a low resistivity, a solid electrolytic capacitor having a lower ESR characteristic.