A capacitor includes a metal case having an opening, a capacitor element accommodated in the metal case, an electrolyte accommodated in the metal case, and a sealing rubber sealing the opening of the metal case. The sealing rubber seals the opening of the metal case while the sealing rubber is compressed to have a stress applied thereto. The stress is not lower than 0.5 MPa and not higher than a predetermined maximum value. This capacitor prevents the electrolyte from leaking, thus having high reliability.