A semiconductor device manufacturing method includes the steps of: forming a transistor on a surface side of a silicon layer of a silicon-on-insulator substrate, the silicon-on-insulator substrate being formed by laminating a substrate, an insulating layer, and the silicon layer; forming a first insulating film covering the transistor and a wiring section including a part electrically connected to the transistor on the silicon-on-insulator substrate; measuring a threshold voltage of the transistor through the wiring section; forming a supporting substrate on a surface of the first insulating film with a second insulating film interposed between the supporting substrate and the first insulating film; removing at least a part of the substrate and the insulating layer on a back side of the silicon-on-insulator substrate; and adjusting the threshold voltage of the transistor on a basis of the measured threshold voltage.