The calculation unit converts into a battery age each parameter calculated for a different factor of degradation of a battery. If at least one of the battery ages has reached an upper limit age, the determination unit determines that it is necessary to conduct a battery diagnosis. Once it has been determined that it is necessary to conduct the battery diagnosis, the display control unit causes a display device to display a diagnosis request message. After displaying the diagnosis request message has started if there is no result of the battery diagnosis received the electric power limiter unit limits electric power charged to and discharged from the battery. After the electric power charged to/discharged from the battery is limited if there is no result of the battery diagnosis received the start-up prohibition unit prohibits starting a system driving the vehicle.