Lateral displacement reference positions LXL, LXR are set on left and right from a center in a width direction of a traffic lane L where a vehicle travels. Then, at least in a case where the vehicle is positioned on an inner side of the left and right lateral displacement reference position LXL, LXR, the vehicle is feedback-controlled so as to decrease a yaw angle deviation. Further, in a case where the vehicle is positioned at an outer side of the left and right lateral displacement reference position LXL, LXR with respect to the traffic lane center, the feedback control is performed so as to decrease the angle deviation and a lateral displacement deviation.