A cover window includes glass including a folding portion of a folding area, a planar portion, and a boundary portion between the folding portion and the planar portion, the boundary portion having a thickness that gradually becomes greater than a thickness of the folding portion as farther from the folding portion and having inclination with respect to the planar portion, and a filler disposed on a first surface of the glass. The inclination is an acute angle defined when a virtual line which is parallel to the planar portion and meets the folding portion meets the boundary portion, and is less than about 1°. A difference between a refractive index of the filler and a refractive index of the glass is within about 0.07.