An apparatus for manufacturing a tension mask-frame assembly includes a frame loading unit configured to load a tension mask-frame assembly, a pressing unit configured to press the support frame, a load cell configured to measure a force applied to the support frame, and a control unit configured to control the pressing unit to pre-deform the support frame in accordance with at least a portion of a bending deformation amount of the support frame, caused by own weight of the support frame and tension of the tension mask. The pressing unit includes inward pressing members which press the pair of support frames toward the inside of the frame, and outward pressing members which press the support frame toward the outside of the frame. The outward pressing members are disposed in a slot formed in a lengthwise direction of the support frame.