In a conversion circuit having a plurality of switching elements connected in series and parallel and a capacitor, the respective parts are connected by an external stacked conductor in which a P conductor connected to the positive electrode of the capacitor, an N conductor connected to the negative electrode of the capacitor (2), an AC conductor, and an even number of intermediate conductors connected between the plurality of switching elements, are stacked in plural layers. The respective switching elements are arranged such that the mutual positional relationship between the positive terminals and the negative terminals is the same as a direction of main current flowing through the external stacked conductor. The plurality of switching elements are arranged symmetrically with respect to a center line of the external stacked conductor which is in the same direction as the main current. External connection terminals are provided to the AC conductor, so as to be positioned symmetrically with respect to the center line.