Provided is a thin-film transistor that includes: a substrate; a first barrier film formed on the substrate; a second barrier film formed in a selective region on the first barrier film, and having a barrier property against hydrogen; an oxide semiconductor layer including a first part formed on the second barrier film and a second part formed on the first barrier film, in which the first part functions as an active layer, and the second part has lower electrical resistance than the first part; a gate electrode formed on the first part of the oxide semiconductor layer with a gate insulating film therebetween; and a source electrode or drain electrode electrically connected to the second part of the oxide semiconductor layer. The first barrier film has a barrier property against an impurity from the substrate and a property of chemically reducing the oxide semiconductor layer.