According to one embodiment, a method of manufacturing a thin-film transistor includes forming a semiconductor layer on a gate electrode with an insulating layer 12 being interposed, forming interconnect formation layers on the semiconductor layer, forming a plurality of interconnects and electrodes by patterning the interconnect formation layers through etching, patterning the semiconductor layer in an island shape through etching after forming the electrodes, exposing a channel region of the semiconductor layer by etching a part of the electrodes on the semiconductor layer, and forming a protective layer so as to overlap the interconnects, the electrodes and the semiconductor layer having the island shape.