A sealing method of an organic EL display device which can effectively prevent the organic EL display device from being influenced by moisture and can suppress the manufacturing cost of the organic EL display device is provided. An organic EL element is covered with a resin sheet. The resin sheet is adhered to a sealing substrate and an element substrate on which organic EL elements are formed by lamination. At a peripheral portion of the organic EL display device, between the element substrate and the sealing substrate, an organic seal is filled to a side portion of the resin sheet using an under-filling method, and the organic seal is cured by radiating ultraviolet rays. Due to such constitution, it is possible to realize the highly reliable sealing of the organic EL display devices at a low cost.