A metal mask according to some embodiments of the present disclosure may include a metal thin film having a first thickness and having a first region including a transmission region defining first openings penetrating the metal thin film, and a non-transmission region including an etching portion having a second thickness that is smaller than the first thickness, and a second region adjacent the first region, and defining second openings penetrating the metal thin film, wherein an opening density of the first region is less than an opening density of the second region, the opening density of the first region being defined as a number of the first openings per an area of the first region, and the opening density of the second region being defined as a number of the second openings per an area of the second region.