Disclosed is a method for preparing an organic light-emitting display device in which a substrate and an encapsulation substrate are completely coalesced using a frit. The method for preparing an organic light-emitting display device according to one aspect of the present invention includes a first substrate including an organic light-emitting diode and a second substrate for encapsulating at least a pixel region of the first substrate, the method including applying a first frit paste to surround the pixel region in the first substrate, and applying a second frit paste to be faced against the first frit paste in the second substrate, sintering the first and the second frit pastes to form a first frit and a second frit, respectively, coalescing the first substrate to the second substrate to contact the first frit and the second frit to each other, attaching the first substrate and the second substrate to each other by irradiating a laser or an infrared ray to the first frit and the second frit, both contacted to each other.