A steering mechanism control system is provided with a steering angle ratio varying device, a steering angle determining section, a steering state determining section, a steering reaction force control device and a characteristic setting section. The steering angle ratio varying device controls a ratio of a steered angle of a steerable wheel with respect to a steering input angle in accordance with a steering angle characteristic. The steering angle determining section determines the steering input angle resulting from a steering operation. The steering state determining section determines a steering state based on the steering input angle. The steering reaction force control device controls a steering reaction force in accordance with a reaction force characteristic. The characteristic setting section selectively sets the steering angle characteristic and the reaction force characteristic based on the steering state determined by the steering state determining section.