A manufacturing method of an adhesive layer includes: providing a preliminary adhesive layer, attaching a mask to a first area portion of the preliminary adhesive layer, and thereby, provide a second area portion of the preliminary adhesive layer that is adjacent to the first area portion and to which the mask is not attached, to provide an adhesive layer that exhibits good folding reliability. In addition, a display device may exhibit good folding reliability characteristics by including the adhesive layer from which an adhesion force of a folding area is reduced between a supporting member and a display panel of the display device.