An electric double layer capacitor having an electrode rolled body contained in an outer packaging can is disclosed. The electrode rolled body includes a positive electrode plate having a positive electrode foil, on both sides of which an active substance is applied, a negative electrode plate having a negative electrode foil, on both sides of which the active substance is applied, and a separator interposed between these electrode plates, and is obtained by winding the above parts. The negative electrode foil is electrically connected directly to a bottom of the outer packaging can so that heat generated in an interior of the electric double layer capacitor is efficiently transferred to the outer packaging can from the negative electrode foil. The negative electrode foil has a greater thickness than that of the positive electrode foil, which is not electrically connected to the outer packaging can, so that heat quantity transferred is made large.