A thin film transistor includes, an insulating substrate, a gate electrode provided on an upper surface of the insulating substrate, a gate insulating film formed so as to cover the gate electrode, an oxide semiconductor layer provided on the gate insulating film, a channel protective layer provided at least on an upper surface of the oxide semiconductor layer, and a source electrode and a drain electrode provided so as to come into contact with the oxide semiconductor layer, wherein the channel protective layer is formed such that the film density of a portion provided so as to come into contact with the oxide semiconductor layer is higher than the film density of a portion distant from the oxide semiconductor layer.