When a variable value indicates that a steering characteristic is understeer, a control unit controls a variable transmission ratio device to change a second steering angle such that the greater the understeer indicated by the variable value, the smaller the steering angle of steered wheels relative to the turning angle of a steering wheel becomes. When the differentiated value of the variable value indicates that the understeer is changing to increase, a correction unit corrects the variable value such that the greater the degree of change of the understeer indicated by the differentiated value, the greater the understeer indicated by the variable value becomes. Hence, the attitude of a vehicle in understeer is stabilized with a simple configuration.