A sealing device including a mask for partially irradiating light and a method of manufacturing a display device using the sealing device is disclosed. The sealing device used to bond first and second substrates by interposing a sealing material at edges of the first and second substrates and by irradiating light to the sealing material comprises: a mask disposed on one side of the stage, in which a transmission portion is formed in correspondence to the formation position of the sealing member so that light can be irradiated to the sealing material; and an optical head irradiating the light to the sealing material through the transmission portion of the mask. A pattern for regulating the amount of the light irradiated to the sealing material is formed in the transmission portion of the mask.