A semiconductor device comprising a flat wiring board, a first LSI disposed on one surface of the wiring board, a sealing resin for covering the one surface and a side face of the first semiconductor element, and a second LSI disposed on another surface of the wiring board. The wiring board has conductive wiring as a wiring layer, an insulation resin as a support layer for the wiring layer, and a conductive through-hole that passes through the wiring layer and the support layer. Connection points between lands disposed in positions in which the external peripheral edges of the semiconductor elements transverse the interior of the lands as viewed vertically from above, which lands are selected from land portions on which the external connection terminals are formed, and the wiring board formed in the same plane as the lands, are unevenly distributed toward one side of the wiring board. Connections for very small wiring are thereby made possible, and a plurality of semiconductor elements can be very densely connected.