Provided are an apparatus for manufacturing a mask assembly, a method for calculating auto-teaching data using the same, and a method of manufacturing a mask assembly using position correction values calculated by auto-teaching data calculation. The apparatus for manufacturing a mask assembly includes a processing unit including a stage, a mask, a mask frame, and marking parts, a first gantry disposed on the processing unit and movable in a first direction, a second gantry connected to the first gantry and movable in a second direction intersecting the first direction, a photographing unit connected to the second gantry and that photographs the marking parts, and a movement control unit that controls movements of the first gantry and the second gantry.