Abstract: A wheel-turning device that constitutes a steer-by-wire steering system is made as compact as possible so as to be housed in a wheel house of a vehicle. The steer-by-wire steering system is provided including a wheel-turning device mechanically separated from a steering input device, the wheel-turning device being controlled based on an input signal from the steering input device, wherein the wheel-turning device includes a wheel-turning motor secured to a knuckle of a steered wheel via a gear case, a wheel-turning shaft secured to an upper arm, a worm wheel secured to the wheel-turning shaft, a worm gear meshing with the worm wheel, and the gear case housing the gears.