Disclosed herein is a full-size mask assembly and a manufacturing method thereof. The full-size mask assembly according to an embodiment of the present invention includes a frame having a frame opening formed therein and a support surrounding the frame opening, a structural auxiliary mask supported by the support and having a plurality of shafts in a grid shape to form a plurality of structural auxiliary mask openings, and a plurality of cell unit masks supported by the structural auxiliary mask and each of which has a deposition pattern portion through which a deposition material passes.