An electric double layer capacitor is provided with a cell, in which a pair of polarizable electrodes, which are impregnated with an electrolyte, are disposed in opposition on either side of a separator; wherein the polarizable electrodes are provided with collector electrodes, and a peripheral portion of the cell is sealed by a sealing member composed of synthetic resin. The collector electrodes are composed of an alloy made of crystal grains of differing components and the collector electrodes pass through the sealing member while in intimate contact with the sealing member, extending to the outside of the sealing member. A metal plated layer made of crystal grains of a single component is formed on those locations on the collector electrodes that pass through the sealing member.