Provided is a thin film transistor which is provided with an oxide semiconductor thin film layer and has a threshold voltage that does not change much due to light, a bias stress or the like, thereby exhibiting excellent stress resistance. A thin film transistor of the present invention is provided with: a gate electrode; a single oxide semiconductor layer that is used as a channel layer; an etching stopper layer for protecting the surface of the oxide semiconductor layer; a source/drain electrode; and a gate insulating film that is arranged between the gate electrode and the channel layer. The metal elements that constitute the oxide semiconductor layer are In, Zn and Sn. The hydrogen concentration in the gate insulating film, which is in direct contact with the oxide semiconductor layer, is controlled to 4 atom% or less.