To provide a method of manufacturing a waterproof and reliable semiconductor device.

On a substrate, an element formation layer is formed consisting of a plurality of thin-film integrated circuits. After pasting an adhesive member on one face of the element formation layer, the element formation layer is peeled off from the substrate, and then the element formation layer and adhesive member are divided into a plurality of thin-film integrated circuits pasted with the adhesive members. Thereafter, a first flexible board is pasted to the other face of the thin-film integrated circuits, and the adhesive member is peeled off from the one face of the thin-film integrated circuits. Then, a second flexible board is pasted to the one face of the thin-film integrated circuits and to an exposed part of the first flexible board. Division is performed in a region where the first and second flexible boards are in contact.