PURPOSE: To obtain a large steering angle with a small amount of steering in a low speed range and not to be sensitive in a high speed range by providing a second rotation/straight line converting means for converting the rotary motion of a rotary member to the recilinear motion of a second axial displacement member connected to a steering wheel.

CONSTITUTION: The steering input from a steering wheel 1 is input to a rotation/straight line converting means U, and the converted rectilinear displacement of a rectilinear motion member is input to a straight line/rotation varying means V. The straight line/rotation varying means V is capable of changing the relation of the axial displacement of the rectilinear displacement member to the rotating angle of a rotary member. The rotation angle of the rotary member is converted to the axial displacement by a second rotation/straight line converting means W for converting the rotary displacement to the rectilinear displacement and given to a wheel 8 to be converted to a steering angle. That is, the axial displacement is varied while the maximum steering angle of a steering wheel is fixed and the rotating angle of the rotary member is fixed, whereby the maximum steering angle of the steering wheel can be varied.