A metal mask manufacturing method includes: (a) disposing a first anti-etching layer having a first void region on a first face of a substrate; (b) disposing a second anti-etching layer on a second face of the substrate opposite to the first face, wherein a second void region of the second anti-etching layer is corresponding to the first void region; (c) performing a first etching on the first face and the second face to form a first concave part and a second concave part separated by a part of the substrate; (d) disposing a protecting layer filled into the first concave part; (e) performing a second etching from the second face to produce a void between the first concave part and the second concave part; (f) removing the second anti-etching layer; and (g) performing a third etching from the second face.