The present invention relates to a photoelectric coal and gangue sorting device and a sorting method therefor. The device comprises a support frame, a coal and gangue separation screen body, a sealing upper cover, a sieving mechanism, a driving mechanism, a separating and conveying mechanism, a positioning plate and a sorting unit; the coal and gangue separation screen body, on the top of which is provided with the sealing upper cover and inside of which is provided with the separating and conveying mechanism, is fixedly installed on one side of the support frame by means of bolts; the side wall of the positioning plate, which is arranged above the separating and conveying mechanism, is fixed to the inner wall of the coal and gangue separation screen body by means of spot welding.