In an engine automatic-stop/restart system according to the present invention, in the case where an engine self-restoration determination unit determines that an engine can autonomously be restored, fuel supply by a fuel injection control unit is resumed so that the engine is autonomously restored; and in the case where the engine self-restoration determination unit determines that the engine cannot autonomously be restored, the fuel supply by the fuel injection control unit is resumed, and based on an engine rotation speed detected by the engine rotation speed detection unit, a pinion gear rotation speed detected by the pinion gear rotation speed detection unit, and the result of determination by the engine self-restoration determination unit, there is performed the energization or de-energization of the pinion gear driving unit and the starter motor.