The battery control device includes: a state detecting means which receives electric power from an on-vehicle low-voltage battery having a supply voltage lower than that of an on-vehicle high-voltage battery composed of a plurality of unit cells connected together in series and detects a state of the on-vehicle high-voltage battery to monitor the on-vehicle high-voltage battery; an equalizing means for equalizing a voltage of each unit cell; and a control means which receives electric power from the on-vehicle low-voltage battery and starts to control the equalizing means in response to turning-off of an ignition switch, wherein the control means cuts electric power supplied from the on-vehicle low-voltage battery to the state detecting means after the turning-off of the ignition switch and before the control means starts to control the equalizing means.