A starting device is used in a starting system that includes a starting electric motor unit and a rotating electrical machine; the starting electric motor unit including a motor that rotates a pinion gear, and a pushing member that pushes out the pinion gear toward a ring gear, the ring gear rotating together with a crankshaft of an engine; the rotating electrical machine being connected to the crankshaft and rotating the crankshaft; the starting system being configured to push, using the pushing member, the pinion gear toward the ring gear, and drive the motor to rotate, based on driving force of the motor, the ring gear via the pinion gear, thus starting the engine. The starting device includes a drive instruction unit that instructs the rotating electrical machine to rotate the ring gear via the crankshaft during a pre-drive period before drive of the motor.