Disclosed herein is a flexible display device including a display panel displaying an image, a touch screen panel on the display panel, and a window substrate covering the touch screen panel. The window substrate includes: a flexible base layer including a first surface facing an outside and a second surface facing the display panel in an opposite direction to the first surface; and a coating layer having hardness higher than that of the base layer and having a plurality of coating tiles arranged on the first surface of the base layer thereof, each coating tile being spaced from adjacent ones of the coating tiles.