Disclosed is an aluminum electrolytic capacitor, which comprises a capacitor element prepared by rolling an anode foil and a cathode foil together with a separator and impregnating them with a driving electrolyte, an anode lead electrically connected to the anode foil, a cathode lead electrically connected to the cathode foil, a tubular metal case having one closed end and the other open end and containing the capacitor element, and a sealing member hermetically closing the open end, wherein the anode and cathode leads are bent along an outer surface of the sealing member. In this aluminum electrolytic capacitor, the sealing member is comprised of a rubber composition containing a rubber component having, as a constituent, a butyl rubber prepared by crosslinking an isobutylene-isoprene copolymer having an unsaturation degree of 1.2 to 2.5 mol %, with an alkyl-phenol-formaldehyde resin, and 100 to 200 mass parts of reinforcing filler with respect to 100 mass parts of the rubber component. The rubber composition has a Wallace hardness according to International Rubber Hardness Degree (IRHD) of 80 Hw or more, and a tensile elastic modulus at a solder reflow temperature of 4 N/mm.sup.2 or more.