A battery characteristic detecting method according to the invention includes a first step in which constant current discharge from a battery is performed at a predetermined current value, and a voltage during constant current discharge is measured; a second step in which overpotential for mass transfer control in the battery or resistance for the mass transfer control in the battery is calculated based on the voltage measured in the first step; and a third step in which a determination that a characteristic change has occurred in the battery is made, when the overpotential for the mass transfer control in the battery or the resistance for the mass transfer control in the battery calculated in the second step is larger than a predetermined threshold value.