An organic light-emitting display device comprising: a lower substrate; an upper substrate facing the lower substrate; an adhesive layer between the lower substrate and the upper substrate, a display area including a thin-film transistor and an organic light-emitting element on the lower substrate; a bezel area configured to surround the display area; a transparent encapsulation unit including at least a first encapsulation layer, a first cover layer and a second encapsulation layer; and a first buffer layer, wherein the first buffer layer is configured to reduce the space between the upper substrate and the lower substrate at the bezel area such that the adhesive layer fills up the reduced space at the bezel area, wherein the first encapsulation layer is formed on the organic light-emitting element and covers the display area and the bezel area, wherein the first cover layer is formed on the first encapsulation layer and covers the display area and at least a portion of the bezel area adjacent to the display area, wherein the first buffer layer is formed laterally spaced apart from the first cover layer and on the first encapsulation layer and is further formed to cover at least another portion of the bezel area, the at least another portion being spaced apart from the portion of the bezel area covered by the first cover layer, and wherein the second encapsulation layer, which covers the first cover layer and the first buffer layer, is in contact with the first encapsulation layer at a contact surface of the first encapsulation layer and the second encapsulation layer between the first cover layer and the first buffer layer, and wherein the first buffer layer is made of the same material as the first cover layer, wherein the adhesive layer is configured to fill the space between the transparent encapsulation unit and the upper substrate in the display area and the bezel area. a lower substrate; an upper substrate facing the lower substrate; an adhesive layer between the lower substrate and the upper substrate, a display area including a thin-film transistor and an organic light-emitting element on the lower substrate; a bezel area configured to surround the display area; a transparent encapsulation unit including at least a first encapsulation layer, a first cover layer and a second encapsulation layer; and a first buffer layer, wherein the first buffer layer is configured to reduce the space between the upper substrate and the lower substrate at the bezel area such that the adhesive layer fills up the reduced space at the bezel area, wherein the first encapsulation layer is formed on the organic light-emitting element and covers the display area and the bezel area, wherein the first cover layer is formed on the first encapsulation layer and covers the display area and at least a portion of the bezel area adjacent to the display area, wherein the first buffer layer is formed laterally spaced apart from the first cover layer and on the first encapsulation layer and is further formed to cover at least another portion of the bezel area, the at least another portion being spaced apart from the portion of the bezel area covered by the first cover layer, and wherein the second encapsulation layer, which covers the first cover layer and the first buffer layer, is in contact with the first encapsulation layer at a contact surface of the first encapsulation layer and the second encapsulation layer between the first cover layer and the first buffer layer, and wherein the first buffer layer is made of the same material as the first cover layer, wherein the adhesive layer is configured to fill the space between the transparent encapsulation unit and the upper substrate in the display area and the bezel area.