PURPOSE:To prevent the gas of driving electrolyte from flowing out, by installing a temperature detecting element on an aluminum rivet for fixing a pair of metal terminals to an aperture sealing plate, which terminals are connected with a pair of leading-out lead wires led out from a capacitor element. CONSTITUTION:When an excessive voltage higher than or equal to a rated voltage is applied to an aluminum electrolytic capacitor, the leak current of a capacitor element 11 increases, and the internal temperature of an armoring case 16 rises, on account of Joule heat due to the resistance of driving electrolyte and a dielectric oxide film. The heat of the temperature rise is conducted to an aluminum rivet 15, via a pair of leading-out lead wires, and detected by a temperature detecting element 18 fixed on the aluminum rivet. The detected signal of the element 18 is sent to the outside, and the electric circuit of the capacitor is cut off by the external signal. Thereby the gas of driving electrolyte can be prevented from flowing out to the outside.