An electrical double layer capacitor having an electrolyte-containing layer between a first polarizable electrode layer and a second polarizable electrode layer. An insulating adhesive portion adheres to a first current collector and a second current collector and extends around the first and second polarizable electrode layers and the electrolyte-containing layer. A thickness of the insulating adhesive portion is larger than a sum of thicknesses of the first and second polarizable electrode layers and the electrolyte-containing layer.