A described technology relates generally to a thin-film deposition mask assembly of a flat panel display for correcting form distortion caused by tension of a division mask. The thin-film deposition mask assembly includes: a frame for forming a penetrated opening; a first change compensating member and a second change compensating member disposed across the opening, fixed to a free end member formed by partially cutting the frame from the opening, and arranged as a pair; and a plurality of division masks being disposed to cross the first change compensating member and the second change compensating member on top sides of the first change compensating member and the second change compensating member.