Semiconductor device including semiconductor layer, first impurity region on surface layer portion of semiconductor layer, body region at interval from first impurity region, second impurity region on surface layer portion of body region, field insulating film at interval from second impurity region, gate insulating film on surface of the semiconductor layer between second impurity region and field insulating film, gate electrode on gate insulating film, first floating plate as ring on field insulating film, and second floating plate as ring on same layer above first floating plate. First and second floating plates formed by at least three plates so that peripheral lengths at centers in width direction thereof are entirely different from one another, alternately arranged in plan view so that one having relatively smaller peripheral length is stored in inner region of one having relatively larger peripheral length, and formed to satisfy relational expression: L/d=constant.