An electric double layer capacitor capable of preventing leakage of an electrolytic solution from the inside and interfusion of unnecessary material from the outside, and capable of forming insulation between a terminal and an outer casing, is provided. A lower-insulation ring 131 is fit into a terminal 112 until the lower-insulation ring comes in the upper side of a flange portion 113. Then, the terminal 112 in this state is inserted into a center of the through hole 111a of a sealing plate 111 from the inside of an outer casing 121. Then, an O-ring 133 is press fit into a spacing 135 formed by a cylindrical portion 112a and the through hole 111a. Further, an upper-side insulation ring 137 is fit to the upper side of this press fit O-ring 133. Then, a setting spring 139 is attached to the terminal 112 so as to press down the upper-side insulation ring 137.