An electrical double layer capacitor is provided which is capable of ensuring its reliability and providing increased energy density per unit volume of a capacitor. A negative electrode is so configured as to cover all surfaces of a positive electrode and, therefore, there is no portion in which the positive electrode does not face the negative electrode, which enables generation of gas within the capacitor to be suppressed and ensures reliability of the capacitor. Portions in which the negative electrode do not face the positive electrode serve as non-covered portions and, therefore, electrostatic capacitance per unit volume of electrodes is made to increase, and energy density is improved.