An organic light-emitting display device has improved transmittance and UV light reliability by optimizing the thickness and material of a cathode. An organic light-emitting display device comprises an organic light-emitting element on a substrate, the organic light-emitting element including an anode, an organic light emitting layer, and a cathode, an organic layer between the substrate and the organic light-emitting element, and an auxiliary layer adjacent to the cathode and including a material having electron injection ability, such that the influence of UV lights on the OLED device is reduced, thereby improving the efficiency and lifespan of the organic light-emitting element.