An electrical storage device having a positive electrode, a negative electrode, a lithium electrode, and an electrolyte capable of transferring lithium ion, the lithium electrode is out of direct contact with the negative electrode, and lithium ion is supplied to the negative electrode by flowing a current between the lithium and negative electrode through an external circuit. A method of using the electrical storage device includes using the lithium electrode as a reference electrode, the positive electrode potential and negative electrode potential is measured, and the potential of the positive or negative electrode is controlled during charging or discharging. The potentials of the positive electrode and negative electrode are monitored to easily determine whether deterioration of the electrical storage device is caused by the positive or negative electrode. It is possible to control the device with the potential difference between the negative electrode and reference electrode, using the negative potential.