Provided is a control device for a secondary battery that uses, as a positive-electrode material, a positive-electrode active material having different open-circuit voltage curves during charging and discharging. This control device for a secondary battery includes: a determination means for determining, on the basis of the charging/discharging state of the secondary battery, whether calculating the current SOC of the secondary battery is possible; and a charging control means for charging the secondary battery until a predetermined fully charged state is reached if the determination means determines that calculating the current SOC of the secondary battery is not possible.