A semiconductor device comprising: a cooling metal plate; a plurality of high voltage side semiconductor switching elements that are electrically connected parallel to each other and fixed in a line on one surface of the cooling metal plate, each of said plurality of high voltage side semiconductor switching elements having an attached high voltage side interconnect conductor (9, 10, 11, 12); a plurality of low voltage side semiconductor switching elements that are electrically connected parallel to each other and fixed in a line on one surface of the cooling metal plate, each of said plurality of low voltage side semiconductor switching elements having an attached low voltage side interconnect conductor (9, 10, 11, 12); a positive polarity side terminal and a negative polarity side terminal for receiving DC electric power; an output terminal for outputting AC electric power; and a multilayered conductor (5, 7) that has a positive side conductive plate and a negative side conductive plate which are disposed to oppose each other with an insulative material interposed; wherein the positive side conductive plate and the negative side conductive plate are electrically connected to the positive polarity side terminal and the negative polarity side terminal, respectively; the plurality of high voltage side semiconductor switching elements are laid out in a line along the multilayered conductor; one of said high voltage side interconnect conductors is connected to the positive side conductive plate; the remaining high voltage side interconnect conductors are connected to the output terminal; the plurality of low voltage side semiconductor switching elements are laid out in a line along the multilayered conductor (5, 7); one of said low voltage side interconnect conductors is connected to the output terminal, respectively; and the remaining low voltage side interconnect conductors are connected to the negative side conductive plate; the high voltage side and low voltage side semiconductor switching elements are divisionally arranged into two groups of switching elements, respectively; and the multilayered conductor (5, 7) and the output terminal are arranged between the two groups of switching elements. a cooling metal plate; a plurality of high voltage side semiconductor switching elements that are electrically connected parallel to each other and fixed in a line on one surface of the cooling metal plate, each of said plurality of high voltage side semiconductor switching elements having an attached high voltage side interconnect conductor (9, 10, 11, 12); a plurality of low voltage side semiconductor switching elements that are electrically connected parallel to each other and fixed in a line on one surface of the cooling metal plate, each of said plurality of low voltage side semiconductor switching elements having an attached low voltage side interconnect conductor (9, 10, 11, 12); a positive polarity side terminal and a negative polarity side terminal for receiving DC electric power; an output terminal for outputting AC electric power; and a multilayered conductor (5, 7) that has a positive side conductive plate and a negative side conductive plate which are disposed to oppose each other with an insulative material interposed; wherein the positive side conductive plate and the negative side conductive plate are electrically connected to the positive polarity side terminal and the negative polarity side terminal, respectively; the plurality of high voltage side semiconductor switching elements are laid out in a line along the multilayered conductor; one of said high voltage side interconnect conductors is connected to the positive side conductive plate; the remaining high voltage side interconnect conductors are connected to the output terminal; the plurality of low voltage side semiconductor switching elements are laid out in a line along the multilayered conductor (5, 7); one of said low voltage side interconnect conductors is connected to the output terminal, respectively; and the remaining low voltage side interconnect conductors are connected to the negative side conductive plate; the high voltage side and low voltage side semiconductor switching elements are divisionally arranged into two groups of switching elements, respectively; and the multilayered conductor (5, 7) and the output terminal are arranged between the two groups of switching elements.