A flexible display device including a display panel configured to display 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; a first coating layer having hardness higher than that of the base layer and having a plurality of first coating tiles arranged on the first surface of the base layer thereof, at a first gap from each other; and a second coating layer having hardness higher than that of the base layer and having a plurality of second coating tiles arranged on a layer different from the first surface of the base layer thereof, at a second gap from each other.