A supporting device is adapted to be mounted on a bicycle wheel and includes a central cap unit, a plurality of end seats, and a plurality of covering units. The bicycle wheel includes a hub and a wheel rim. The central cap unit is sleeved fixedly on the hub and has coupling portions. The end seats are connected fixedly on the wheel rim, and are formed respectively with coupling sections registered respectively with the coupling portions. Each of the covering units has an inner end portion connected to a respective one of the coupling portions of the central cap unit and an outer end portion connected to one of the coupling sections of the end seats that is registered with the respective one of the coupling portions, so as to enhance a structural strength of the bicycle wheel.