Abstract: Disclosed is an electric double layer capacitor, including a unit cell of completely combined polarizable electrodes and metal cases, and a fabrication method thereof. The method includes the steps of pitting or etching any one face of a metal substrate made of the same material as the metal cases to form a plurality of indentations, coating slurry of an electrode material consisting mainly of an activated carbon powder onto the indented face of the metal substrate, compressing the coated face by use of a heating roll to afford the polarizable electrodes, and welding the polarizable electrodes and the metal cases after aligning the centers thereof with each other. In the thusly fabricated electric double layer capacitor, the electrode material of the activated carbon powder is combined with the metal case through the metal substrate adhered to the metal case by welding.