To provide a steering system of a vehicle with variable transmission ratio free of a drop of the steering feeling such as an increase in the steering torque even in case a failure has occurred in a reduction gear.

The steering system with variable transmission ratio is equipped with an actuator housing 31a installed stationarily on a column frame 7 and a transmission ratio changing motor 32 and the reduction gear 35 installed inside the actuator housing 31a. Further torque controlling means 92 and 93 are installed to couple fast the actuator housing 31a with the column frame 7 in case a torque below the specified level is applied to the actuator housing 31a and disengage the actuator housing 31a from the column frame 7 in case a torque equal to or above the specified value is applied to the actuator housing 31a.