A method and a device are provided for estimating a remaining capacity of a battery. Transient characteristics are generated that represent a correlation between the remaining capacity and a closed circuit voltage, the correlation transitioning from one of a charging-side and a discharging-side characteristic to the other when the charging/discharging of the battery has been switched, on the basis of map data of a charging-side characteristic that is only conducted from a fully-discharged to a fully-charged state and a discharging-side characteristic that is only conducted from the fully-charged to the fully-discharged state, the characteristics representing a correlation between the remaining capacity and the Closed Circuit Voltage of the battery. When charging and discharging of the battery have been switched, the remaining capacity of the battery is estimated from the Closed Circuit Voltage of the battery by using the transient characteristics until polarization of the battery enters a saturated state.