An electric double layer capacitor comprises an electrode, a current collector, an electrolyte, a separator, a concave-shaped container for accommodating them, and a sealing plate for sealing an opening part of the container, wherein the sealing plate is fitted inside the container. By having a structure fitting the sealing plate inside an opening part of the concave-shaped container, the positioning between the sealing plate and the container becomes easy, and the displacement of the sealing plate in the horizontal direction can be reduced. Thus, the decline of the yield can be prevented.