The spin transistor in accordance with the present invention comprises a magnetoresistive element having a fixed layer, a free layer, and a semiconductor layer provided between the fixed layer and free layer; a source electrode layer electrically connected to one end face in a laminating direction of the magnetoresistive element; a drain electrode layer electrically connected to the other end face in the laminating direction of the magnetoresistive element; and a gate electrode layer laterally adjacent to the semiconductor layer through a gate insulating layer provided on a side face of the semiconductor layer.