To optimally secure the stability of a vehicle body at the time of turning a steering wheel is accordance with the vehicle speed and the inclining state of the road, by providing a control device that changes the extent of car speed limit for the turned angle of a steering wheel in accordance with the output of a vehicle speed detecting means.

A signal processing device 4 functions as a control device that limits the vehicle speed based on the output V of a rotary sensor 3, the turned angle of a steering wheel Vk, and the output I of a current detecting circuit 5. This structure limits the car speed comparatively moderately when the speed is slow and comparatively severely when it is high. Also, on an uphill, for example, speed limit becomes comparatively moderate where the consumed current of a motor increases, while it does comparatively severe where the consumed current of the motor decreases. As a result, the stability of the vehicle body at the time of turning steering wheel can optimally be secured in accordance with the vehicle speed and the inclining state of the road.