NOVELTY - The apparatus has a voltage detection circuit electrically connected with an electrical storage element for detecting voltage of two ends of the electrical storage element. The voltage detection circuit and a control circuit are electrically connected with a switch. The control circuit controls on-off operation of the switch by calculating time ratio from real resistance value and adjustment target resistance value of a resistor during a fixed adjustment period. A positive electrode terminal and a negative electrode terminal are connected to two ends of an electrical storage part.    USE - Electrical storage apparatus for use as an emergency electrical storage apparatus, to store electric power in an electrical storage element i.e. electrochemical capacitor, in a motor to drive a fuel-efficient vehicle e.g. hybrid vehicle and electric vehicle, in an outdoor environment. Can also be used for an emergency power source to store electric power in an electrical double layer capacitor.    ADVANTAGE - The control circuit controls on-off operation of the switch by calculating the time ratio from the real resistance value and the adjustment target resistance value of the resistor during the fixed adjustment period based on change of voltage of ends of the electrical storage element and capacitance of the electrical storage element, thus increasing precision of the time ratio, and reducing voltage variation with high precision, and hence prolonging the life span of the apparatus.    DESCRIPTION OF DRAWING(S) - The drawing shows a flowchart illustrating on-off operation of a switch in an electrical storage apparatus.'(Drawing includes non-English language text)'    Step for reading voltage of two ends of electrical storage elements from voltage detection circuits by control circuit before measurement period (S10)    Step for judging passing of measurement period (S20)    Step for calculating energy width of electrical storage elements (S33)    Step for calculating threshold-energy width in obtained energy width (S35)    Step for judging charging energy difference (S41)