A foldable display device is discussed, which is to be switched between a folded state and an unfolded state, the foldable display device including adjustable support units to support a display panel of the foldable display device together with an inner surface of set frames in the unfolded state, the adjustable support units being connected to a hinge unit to enable the adjustable support units to retreat to the inner surface of the set frames in the folded state. In the unfolded state, the adjustable support units and the set frames support the entire area of the display panel to be flat to reduce damage of the display panel.