A thin film transistor includes: a gate electrode and a pair of source-drain electrodes provided on a substrate; an oxide semiconductor layer provided between the gate electrode and the pair of source-drain electrodes, the oxide semiconductor layer forming a channel; a protection film provided over whole of a surface above the substrate; and a gate insulating film provided on a gate electrode side of the oxide semiconductor layer, the gate insulating film having end faces part or all of which are covered with the pair of source-drain electrodes or with the protection film.