Disclosed is a frit sealing apparatus and method of using the same, the apparatus being capable of irradiating infrared rays only to a frit portion of a substrate. The apparatus includes a first chamber, a second chamber positioned inside the first chamber, a lamp positioned inside the second chamber, a stage positioned outside the first chamber to receive and fix a first mother substrate and a second mother substrate, an emitting part formed in the first chamber and the second chamber and positioned to direct heat supplied by the lamp to the stage. The apparatus also includes a mask positioned over the substrates, the mask including one or more transmitting portions positioned over regions containing the frit, and one or more interrupting portions positioned at other regions.