This thin film transistor comprises, on a substrate, at least a gate electrode, a gate insulating film, an oxide semiconductor layer, a source-drain electrode, and two or more protective films. The oxide semiconductor layer comprises Sn, O and one or more elements selected from the group consisting of In, Ga and Zn. In addition, the two or more protective films are composed of at least a first protective film that is in contact with the oxide semiconductor film, and one or more second protective films other than the first protective film. The first protective film is a SiOx film having a hydrogen concentration of 3.5 atomic % or lower.