In a steering device for an outboard engine, a drive shaft of a helm mechanism and an output shaft of an electric assist mechanism are disposed orthogonally to a steering output shaft of a steering operation member. Where the steering operation member is a tiller handle, a torque sensor, provided between an outboard engine body and the tiller handle, detects, as steering torque, a difference between steering angles of the engine body and the tiller handle, and the helm mechanism, drivable by the assist mechanism, operates to compensate for the difference between the steering angles. The assist mechanism and the helm mechanism are provided on the body of the boat.