A solid electrolytic capacitor is provided in which volume efficiency of its capacitor element is improved. A converting substrate having an anode terminal forming portion and cathode terminal portion obtained by forming notches on faces exposed on outside faces of the anode and cathode portions and performing plating in the notches in portions in which the anode and cathode portions of a lower-face electrode type solid electrolytic capacitor is connected to the capacitor element and, after a sheathing resin is formed therein, the sheathed portion and converting substrate are cut along cutting planes to form fillet forming faces on the outside faces of the anode portion and cathode portion of the lower-face electrode type solid electrolytic capacitor.