A photosensor includes a first light-shielding layer provided on an insulating surface; a first insulating layer covering the first light-shielding layer; a semiconductor layer provided on the first insulating layer, the semiconductor layer being connected to a first electrode and a second electrode, and the semiconductor layer configuring a diode; a second insulating layer covering the semiconductor layer; an opening provided in the second insulating layer so as to surround the semiconductor layer as viewed from a planar direction and the opening reaching at least the first insulating layer; and a second light-shielding layer covering at least a side wall of the opening.