A semiconductor device includes a light-emitting element array including plural light-emitting elements and being formed on a semiconductor substrate, a switching element array formed on the semiconductor substrate monolithically with the light-emitting element array, and including switching elements laid out in a matrix form and each having an input end, an output end and a control end with one of the input end and the output end being connected to any one of the plural light-emitting elements, first connection means for connecting the control end of each of the plural switching elements disposed in the same column or the other of the input end and the output end thereof to a first external connection end different per the same column, and second connection means for connecting the control end of each of the plurality of switching elements disposed in the same column or one side of the other of the input end and the output end thereof not being connected to the first external connection end to a second external connection end different per the same row.