In a driving assistance system having an actuator (16) for steering steered wheels of a vehicle, a positional deviation detecting unit (9) detects a deviation of a position of the vehicle from a forward travel path of the vehicle based on information around the vehicle. A steering control variable determination unit (2) determines a steering control variable to cancel the deviation. If a vehicle speed detected by a vehicle speed detecting unit is equal to or greater than a predetermined speed, the steering control variable determined by a steering control variable determination unit (2) decreases with an increase of the vehicle speed under the condition that the deviation of the position of the vehicle from the forward travel path is same. The driving assistance system can reduce a driver's discomfort caused by the steering control through the actuator (16) when the vehicle is running at a high speed.