To provide a structure capable of controlling always safely various devices for vehicle stabilization such as ABS or TCS by measuring accurately a torque, a road reaction force or the like applied to wheels at the braking time or at the acceleration time.

A piezoelectric element 24 is installed between each ring-shaped recessed part 25a, 25b formed respectively on a fitting flange 15 and a rotor 2 constituting a hub 8, to thereby enable to measure the torque, the road reaction force or the like applied to the wheels. Grinding is applied respectively to each bottom face 26, 26 of the ring-shaped recessed parts 25a, 25b, to thereby refine each bottom face 26, 26 into a smooth face. Various devices for vehicle stabilization such as ABS or TCS can be controlled always safely by this constitution.