A steering system for vehicles comprising a steering wheel, a front steering sub-system including a drive pinion interlocked to be rotatable with the steering wheel, a rack shaft having a first rack engaged with the drive pinion and a second rack separated from the first rack, and a driven pinion engaged with the second rack; and a rear steering sub-system including an input shaft operatively connected to the driven pinion, an off-centered pin provided at one end of the input shaft, a pair of rear tie-rods adapted each respectively to turn either of the rear wheels, and a joint member relatively rotatably connected to the off-centered pin and both of the rear tie-rods. The joint member has a longitudinal axis thereof extending transversely of the vehicle. The axis of the off-centered pin is located substantially on the longitudinal axis. The rear tie-rods are connected to the joint member substantially on the longitudinal axis substantially at the same level as the axis of the off-centered pin.The steering system may further comprise an engagement adjustment mechanism for adjusting the engagement between at least either of the pinions and one of the racks associated therewith, the adjustment mechanism being constituted with a gear box having accommodated therein the drive pinion, the rack shaft, and the driven pinion, an off-centered ring being interposed between the inner circumference of the gear box and the outer circumference of the rack shaft, and a rotating mechanism for rotating the off-centered ring.