Provided is an engine starting device enabling the meshing engagement of a pinion gear and a ring gear to be quickly and quietly achieved in an automatic idle-stop system while an engine is rotating by inertia. The engine starting device includes: a ring gear connected to a crankshaft of an engine; a starter motor for starting the engine; a pinion gear for transmitting rotation of the starter motor to the ring gear; pinion-gear moving portion for moving the pinion gear so as to achieve meshing engagement with the ring gear; and starter control portion for executing any one of a plurality of control modes.