A semiconductor device (1A, 1B) comprising: a substrate; a three-terminal light emitting element array provided on said substrate and including a plurality of three-terminal light emitting elements which are substantially linearly arranged, each of said plurality of three-terminal light emitting elements including a first terminal, a second terminal and a third terminal, said third terminal being used to control a current between said first and second terminals (26, 23); and a lead-out wiring portion connected to said plurality of three-terminal light emitting elements, wherein said lead-out wiring portion includes an anode lead-out wiring portion, a gate lead-out wiring portion, and a cathode lead-out wiring portion; wherein said three-terminal light emitting element array includes a common layer formed of a semiconductor layer and provided throughout two or more three-terminal light emitting elements adjacent to each other, said common layer mutually connecting said second terminals of said two or more three-terminal light emitting elements; wherein said three-terminal light emitting element array further includes a plurality of electrodes each of which is disposed on said common layer and disposed between said three-terminal light emitting elements adjacent to each other; wherein each of said plurality of electrodes is equally distanced from said three-terminal light emitting elements adjacent thereto; wherein said plurality of three-terminal light emitting elements and said plurality of electrodes are arranged in a straight line along an arranging direction of said plurality of three-terminal light emitting elements; and wherein saidelectrodes connect said lead-out wiring portion and said common layer. a substrate; a three-terminal light emitting element array provided on said substrate and including a plurality of three-terminal light emitting elements which are substantially linearly arranged, each of said plurality of three-terminal light emitting elements including a first terminal, a second terminal and a third terminal, said third terminal being used to control a current between said first and second terminals (26, 23); and a lead-out wiring portion connected to said plurality of three-terminal light emitting elements, wherein said lead-out wiring portion includes an anode lead-out wiring portion, a gate lead-out wiring portion, and a cathode lead-out wiring portion; wherein said three-terminal light emitting element array includes a common layer formed of a semiconductor layer and provided throughout two or more three-terminal light emitting elements adjacent to each other, said common layer mutually connecting said second terminals of said two or more three-terminal light emitting elements; wherein said three-terminal light emitting element array further includes a plurality of electrodes each of which is disposed on said common layer and disposed between said three-terminal light emitting elements adjacent to each other; wherein each of said plurality of electrodes is equally distanced from said three-terminal light emitting elements adjacent thereto; wherein said plurality of three-terminal light emitting elements and said plurality of electrodes are arranged in a straight line along an arranging direction of said plurality of three-terminal light emitting elements; and wherein saidelectrodes connect said lead-out wiring portion and said common layer.