It is disclosed that an electric double layer capacitor includes a plurality of cells each including activated-carbon electrodes disposed on both sides of a separator; a plurality of packing members each disposed at an outer periphery of the cell, each of the plurality of cells and the plurality of packing members being stacked through a charge collector; and both end plates sandwiching the plurality of cells and the plurality of packing members through both collector electrodes, at least one of the end plates being formed with an inlet through which an electrolytic solution is injected. Moreover, the electric double layer capacitor is covered and sealed with an enclosing member. Moreover, the electric double layer capacitor includes an O-ring disposed in the inlet, or alternatively, an edge of the inlet is curved.