Provided is a photodetector including: an organic semiconductor (20) having protrusions; a metal layer (30) added onto the organic semiconductor (20), for promoting at least one of localized plasmon resonance and surface plasmon resonance in which electrons are excited through irradiation of detection light; and a semiconductor (40) forming a junction with the metal layer (30), for allowing electrons excited through the plasmon resonance to pass through the junction (40a) with the metal layer (30).