A photosensor element is provided with a gate electrode disposed on an insulating substrate, a gate insulating film disposed so as to cover the gate electrode, a semiconductor layer disposed on the gate insulating film so as to overlap the gate electrode, and a source electrode and a drain electrode provided on the semiconductor layer so as to overlap the gate electrode and so as to face each other. The photosensor element has the semiconductor layer provided with an intrinsic semiconductor layer in which a channel region is defined and an extrinsic semiconductor layer that is laminated on the intrinsic semiconductor layer such that the channel region is exposed. The extrinsic semiconductor layer protrudes from the drain electrode on the side close to the channel region.