In an electric double layer capacitor, at least three frame-shaped gaskets are stacked. A cell member of a pair of polarized electrodes sandwiching a porous separator is accommodated within a central gasket so as to be sandwiched between a pair of current collectors. Upper and lower frame shaped gaskets are adhered on both side edges of the central gasket such that the current collectors are sandwiched and held with two gaskets confronting to seal the inside of the central gasket. A step portion is formed in an inner peripheral end surface of at least one of the gaskets confronting such that each of the side edges of the collectors is received in this step portion, whereby making it easy to position the current collector in the gasket. This step portion also makes it possible to bond the current collector to the gasket at a low stress. All surfaces of the side edges of the current collectors are contacted with the gaskets to improve the reliability of the electric double layer capacitor by preventing leaking of the electrolytic solution from the capacitor cell under the high temperature environment.