The present invention provides an organic electronic element manufacturing method which provides a low manufacturing cost and excellent performance stability, and specifically an organic electronic element manufacturing method which provides a low manufacturing cost, and minimizes emission unevenness, lowering of emission efficiency and shortening of lifetime due to deterioration of gas barrier property of sealing. The organic electronic element manufacturing method is featured in that it comprises the steps of forming an organic electronic structure composed of a first electrode, at least one organic layer and a second electrode on a flexible substrate, and applying a flexible sealing substrate to the organic electronic structure, followed by heating treatment, wherein a heating temperature, at which the heating treatment is carried out, is less than Tg (glass transition temperature) of the substrate and not less than Tg of the sealing substrate.