A method of manufacturing a mask includes attaching a first mask base substrate and a second mask base substrate to opposite sides of an adhesive layer, forming a photoresist layer on the first and second mask base substrates, exposing and developing the photoresist layer to remove the photoresist layer on effective area at centers of surfaces of the first and second mask base substrates such that the first photoresist layer remains on non-effective areas at edges of surfaces of the first mask base substrate and the second mask base substrate, etching the effective area to form a stepped groove on the first and second mask base substrates, separating the first and second mask base substrates from the adhesive layer, and forming a pattern hole in the effective area of first and second mask base substrates, each with the first stepped groove thereon.