A semiconductor device includes three-terminal light emitting element array provided on a substrate, which includes a plurality of three-terminal light emitting elements which are substantially linearly arranged. Each three-terminal light emitting elements includes a first, second and third terminals. The third terminal is used to control a current between the first and second terminals. A Lead-out wiring portion is connected to the plurality of three-terminal light emitting elements. The three-terminal light emitting element array includes a common layer provided between two or more three-terminal light emitting elements adjacent to each other. The common layer mutually connects the second terminals (or the third terminals) of the two or three three-terminal light emitting elements. The lead-out wiring portion includes wirings led from the common layer and the plurality of three-terminal light emitting elements and extending in a direction substantially perpendicular to an arranging direction of the plurality of three-terminal light emitting elements.