Present invention relates to an electric double-layer capacitor having positive and negative electrodes containing nonporous carbon as an electrode active material. In the nonporous carbon, multiple layers of graphene having an average interplanar spacing d.sub.002 of 0.350 to 0.380 nm have been grown well. The positive and negative electrodes are impregnated with an electrolyte solution. The nonporous carbon is obtained by activating easily graphitizable carbon, which in turn is obtained by calcining needle coke or pitch made infusible. The elctrolyte solution is either a liquid electrolyte having a planar molecular structure or an electrolyte solution consisting of a liquid electrolyte dissolved in an organic solvent.