An adjustable supporting stand includes a main body with a receiving room, a slidable module disposed in the receiving room, a supporting holder assembled on the slidable module, a gear set connected to the supporting holder, and an elastic member disposed on the main body. The gear set has at least one first gear and a second gear, and the first gear is smaller than the second gear. One end of the elastic member is fixed on the main body and another end of the elastic member is connected to the second gear.