An electric double-layer capacitor includes a plurality of electrode elements each having a current collector, a polarized electrode disposed on a surface thereof, and a strip-like current collecting lead extending from an end of the current collector. The electrode elements are stacked as alternately belonging to respective polarities, and the current collecting leads of the electrode elements are stacked into lead assemblies of the respective polarities. A separator is interposed between the stacked electrode elements, and the lead assemblies are connected respectively to electrode terminals. The lead assemblies of respective polarities serve as respective connectors connected to the electrode terminals. Each of the connectors has a flat joint region as at least a portion thereof. The current collecting leads of each of the lead assemblies are integrally joined to each other by the flat joint region by ultrasonic welding before the connector is connected to the electrode terminal. The connectors are joined to the electrode terminals, respectively, through the respective joint region by electron beam welding or laser beam welding.