A state-of-charge estimating apparatus includes at least a first arithmetic unit configured to calculate, as a first estimation value, the present estimation value calculated based on a battery capacity, the last estimation value, and an electric current flowing in and out between a current control apparatus, which controls charge and discharge amounts of a power storage apparatus, and the power storage apparatus, and a second arithmetic unit configured to calculate, during constant current control, as the present value of a second estimation value, an estimation value calculated based on an equivalent circuit model of a battery and a voltage of the battery and, on the other hand, calculate, during constant voltage control, as the second estimation value, the present estimation value calculated taking into account a resistance change of the battery based on the equivalent circuit model of the battery and the voltage of the battery.