The present disclosure provides a folding display device including a flexible display panel; a first case positioned at a periphery of the display panel; a mid-frame positioned adjacent to the display panel and extending co-planar with the display panel; a plurality of holes extending through the mid-frame at a central region of the mid-frame; a second case positioned adjacent to the mid-frame extending co-planar with the mid-frame; and a third case positioned adjacent to the second case and configured to support the second case. The second case has a hinge part overlapping the plurality of holes in the mid-frame. The holes in the mid-frame and a connecting member holding the holes together in the mid-frame provides elasticity, expandability, and pliability to the folding display device. The connecting member also provides durability so that the folded portion endures the numerous folding and unfolding activities by a user of the display device.