In an electric double-layer capacitor, a solution of a quaternary ammonium borofluoride compound in propylene carbonate is used as an electrolyte. The electrode includes alkali-activated carbon made using meso-phase pitch as a starting material, and a conductive filler having a rest potential smaller than that of the alkali-activated carbon in the electrolyte. The amount Fc of conductive filler incorporated in the electrode is set in a range of 10% by weight.ltoreq.Fc.ltoreq.40% by weight. Such electric double-layer capacitor has a large electrostatic capacity and excellent durability.