A mask stage includes a stage inclined with respect to a vertical direction perpendicular to a plane defined by a first direction and a second direction intersecting each other, a plurality of first support units disposed between the stage and a mask frame disposed above the stage, and a plurality of second support units disposed on the stage and being adjacent to a lower side of the mask frame. The lower side of the mask frame extends in a first direction, and the second support units are respectively disposed under end portions of the lower side of the mask frame, which are opposite to each other in the first direction.