The inverter has a plurality of arms for conducting or cutting off a current and each arm has a switching device and a first and a second wiring layer for connecting the switching device. The first and second wiring layers of each arm are respectively formed on insulating substrates, and one face of the switching device is fixed to the first wiring layer, and the second wiring layer and the other face of the switching device are electrically connected by a laminal conductor, and the laminal conductor has a first and a second connection, and the first connection of the laminal conductor is fixed to the other face of the switching device, and the second connection of the laminal conductor is fixed to the second wiring layer.Thereby, a large current of the inverter can be realized and the assembly capacity of the inverter or the vehicle drive unit will be improved.