The invention is a method for manufacturing an organic electronic device sealing body, adhesively integrating an organic electronic device with a sheet-like sealant made of a modified hydrocarbon-based soft resin having an alkoxysilyl group, the method comprising steps of: step [1]: laminating the organic electronic device and the sheet-like sealant to obtain a laminate; step [2]: putting the resulting laminate into a resin bag, degassing the bag, and then sealing the bag containing the laminate; and step [3]: placing the sealed bag under a pressure of 0.1 MPa or higher to adhesively integrate the laminate. One aspect of the invention provides a method for manufacturing an organic electronic device sealing body which allows industrially-advantageous sealing of the organic electronic device including organic functional elements such as an organic EL element and an organic semiconductor element.