A supporting device includes a modular joint assembly, two fixing members respectively installed on two opposite ends of the modular joint assembly, and a resilient sheet fixed on the outer surface of the modular joint assembly and the fixing members. The modular joint assembly includes a plurality of joints buckled in sequence. Each joint has an arced track groove recessed on a side surface thereof and a buckling portion extended from an opposite side surface thereof. An imaginary datum line is defined by connecting a center of circle of each track groove and is located at one side of the resilient sheet away from the modular joint assembly. When any two buckled joints are rotated with respect to each other, the resilient sheet is compressed and a length of the imaginary datum line is unchanged.