The present invention provides a thin film transistor including an oxide semiconductor layer (4) for electrically connecting a signal electrode (6a) and a drain electrode (7a), the an oxide semiconductor layer being made from an oxide semiconductor; and a barrier layer (6b) made from at least one selected from the group consisting of Ti, Mo, W, Nb, Ta, Cr, nitrides thereof, and alloys thereof, the barrier layer (6b) being in touch with the signal electrode (6a) and the oxide semiconductor layer (4) and separating the signal electrode (6a) from the oxide semiconductor layer (4). Because of this configuration, the thin film transistor can form and maintain an ohmic contact between the first electrode and the channel layer, thereby being a thin film transistor with good properties.