A semiconductor device includes a semiconductor element, a plurality of leads electrically connected to the semiconductor element and one of which supports the semiconductor element, a sealing resin covering the semiconductor element and a portion of each leads, and first and second plating layers exposed from the sealing resin. The sealing resin includes a resin side surface facing in a first direction perpendicular to the thickness direction. At least one of the leads has a lead end surface connected to its back surface and flush with the resin side surface. The first plating layer covers the back surface of the lead. The second plating layer covers the lead end surface and projects in the first direction relative to the resin side surface. An edge of the second plating layer overlaps with the first plating layer as viewed in the first direction.