An idling stop device is mounted on a vehicle and automatically stops and starts an engine of the vehicle. A microcomputer has an idling stop function of automatically stopping the engine when a predetermined stop condition is established and automatically starting the engine when a predetermined start condition is established during the stopping of the engine. A detecting unit detects that a power voltage of the microcomputer, which is obtained by dropping a voltage of a battery of the vehicle is lower than a minimum operating voltage of the microcomputer. A storage unit stores voltage reduction information irrespective of a state of the microcomputer if the power voltage is lower than the minimum operating voltage. A power control unit causes a capacitor which stores electric charges corresponding to power for driving a starter motor of the engine to supply power to the starter motor when the engine is started, if the voltage reduction information is stored in the storage unit.