To prevent an expansion of a long side portion of a capacitor element formed in a flat shape.

The electrolytic capacitor comprises a capacitor element wound with an electrode foil to which an internal terminal is connected via a separator, and a cylindrical support member provided at a central portion of the capacitor element; and houses a flat shaped capacitor element formed by compressing the capacitor element. A long side portion of the supporting member formed by compressing the capacitor element is recessed towards the center of the element, and a gap is provided between the long side portion of the support member and an electrode foil corresponding to the long side portion. With this configuration, the gap can absorb an expansion of the long side portion of the capacitor element to prevent the expansion of the capacitor element, thus providing high capacity without shortening the length of the electrode foil thereof.