A foldable display device may include a display panel, a window disposed on a first surface of the display panel, a metal plate disposed on a second surface of the display panel opposite to the first surface, and a functional member disposed between the display panel and the metal plate, the functional member including a first functional layer in which a plurality of holes are formed and a filler filling each of the holes. An elastic modulus of the filler may be greater than an elastic modulus of the first functional layer.