A method for manufacturing a joined body composed of a first substrate and a second substrate joined together by sealing resin material attached to a predetermined area of the first substrate includes: attaching a sheet material to the first substrate so as to cover the predetermined area, the sheet material including a sheet base material and the resin material provided on one main surface of the sheet base material; forming, after the attaching, in the sheet material, a slit by reducing a thickness of the resin material along an outline of the predetermined area; and separating, after the forming, part of the resin material inside the slit from the sheet base material to keep the part of the resin material inside the slit on the predetermined area of the first substrate and not to keep the rest of the resin material outside the slit on the first substrate.