To obtain a charging method in which the capacity of a secondary battery can be discriminated without a need of a terminal for discrimination and in which the time of a timer is set on the basis of a discrimination result.

First, a constant charging current is supplied to a secondary battery which is mounted and attached, and the voltage of the secondary battery is measured at every prescribed time. Then, on the basis of the measured voltage, the inclination of the voltage with reference to the time is computed. After that, the computed inclination is compared with one or a plurality of predetermined threshold values. Then, on the basis of a comparison result, the capacity of the secondary battery is discriminated. After that, on the basis of the discriminated capacity of the secondary battery, the charging time is set.