Disclosed is an electrical energy storage device provided with a metallic casing to receive a bare cell and first and second terminals located outside of the metallic casing corresponding to each electrode of the bare cell, including a plate-like member provided on at least one of the first and second terminals, an inner terminal contacting the plate-like member to form the boundary between the inner terminal and the plate-like member, and a laser welded portion formed along the boundary between the inner terminal and the plate-like member to connect the plate-like member with the inner terminal.