a main unit, including a first shell, a first supporting plate, and an accommodating space, wherein the first supporting plate is disposed on the first shell and has a first supporting surface, and the accommodating space is surrounded and defined by the first shell and the first supporting plate;

a retractable unit, slidably disposed on the main unit along a telescopic axis and changing between a retracted state and an outstretched state with respect to the main unit, and including a second shell, a pivot, and a second supporting plate, wherein the pivot is disposed on one side of the second shell away from the first shell, the second supporting plate is pivotably hung on the pivot and has a second supporting surface, and the second supporting plate is able to be switched between an inclined position and an aligned position with respect to the pivot;

an elastic element with two ends separately disposed on the main unit and the retractable unit;

a constant force spring, including a winding part and a telescopic part, wherein the winding part is disposed on the first shell; and

a flexible display screen, including a fixed end and a free end, wherein the fixed end is disposed on the first supporting plate, the flexible display screen covers the first supporting surface and is wound around the pivot, the free end is fixed to the telescopic part of the constant force spring, and the constant force spring provides constant tension on the flexible display screen;

wherein the pivot and the first shell are closest to each other when the retractable unit is in the retracted state, and the pivot and the first shell are farthest away from each other when the retractable unit is in the outstretched state.