VEHICLE STEERING SYSTEM

A vehicle steering system can keep the comfort of steering feeling for a driver, even in a situation, such as traveling on a cant road or in a crosswind, where a unidirectional-drift behavior of a vehicle occurs, and includes an electric motor, a steering angle sensor, a steering torque sensor, and an EPS_ECU that controls driving power of the electric motor, when the vehicle is traveling straight, based on vehicle information including a steering torque and a steering angle, to perform a control for applying an assist torque to a steering system. The EPS_ECU includes an integrating unit for calculating an integrated torque value obtained by integrating the steering torque, and a steering effort assist controlling unit for performing an anti-unidirectional-drift control over the driving power of the electric motor, when the integrated torque value exceeds the threshold value, so as to cancel the unidirectional-drift behavior of the vehicle.