An engine automatic stop/restart device includes a ring gear which is linked to a crank shaft of the engine, a starter motor which is energized so as to be rotated, a pinion gear which transmits a rotation of the starter motor to the ring gear, and a pinion gear movement unit which is energized so as to move the pinion gear in a direction of the ring gear, whereby the pinion gear is engaged to the ring gear, in a state where the engine automatic stop/restart device automatically stops the engine when an engine automatic stop condition is established, and restarts the engine when an engine restart condition is established, and includes an inertially-rotating-restart-decision unit which permits or prohibits a restart of the engine, which is inertially rotating after the engine is automatically stopped, in accordance with a detection result of an oil temperature of the engine.