A power conversion device comprising: plural 2in1 power modules each having a rectangular cuboid shape defining a long-side direction that is a vertical direction and a short-side direction that is a horizontal direction; a cooler configured to cool the 2in1 power modules; a capacitor facing a first rectangular side of each 2in1 power module, and having a vertical front surface facing the cooler and 2in1 power modules, a vertical rear surface, a left-hand side vertical surface comprising terminals for connection to DC bus-bars, and a right-hand side vertical surface parallel to the left-hand side vertical surface; an L-shaped positive DC bus bar connected to the 2in1 power modules, the positive DC bus bar having an electric power terminal for connection to the capacitor; an L-shaped negative DC bus bar connected to the 2in1 power modules, the negative DC bus bar having an electric power terminal for connection to the capacitor; respective control signal wires connected to the 2in1 power modules; and respective drive circuit boards, located on a same plane, and configured to deliver control signals to the control signal wires; wherein the 2in1 power modules are mounted to the cooler along a vertical direction that is also a long-side direction of the 2in1 power modules; the power conversion device further comprises: plural AC bus bars respectively connected to the 2in1 power modules, each AC bus bar having an output terminal, each AC bus bar extending horizontally parallel to each other on the same plane parallel to the surface of the cooler; the L-shaped positive DC bus bar and L-shaped negative DC bus bar respectively having vertical front portions parallel to the cooler for electrical connection to the power modules and located between the vertical front surface of the capacitor and the AC bus bars and side vertical portions perpendicular to the cooler, the side vertical portions extending parallel to the left-hand side vertical surface of the capacitor, and the side vertical portions respectively containing the electric power terminals for connection to the capacitor; and wherein connections of the control signal wires to the respective drive circuit boards together with the drive circuit boards face the right-hand side vertical surface of the capacitor; and wherein a center line, perpendicular to the vertical direction and the cooler, of the capacitor is located on an upper side of a center line, perpendicular to the vertical direction and the cooler, of the drive circuit boards. plural 2in1 power modules each having a rectangular cuboid shape defining a long-side direction that is a vertical direction and a short-side direction that is a horizontal direction; a cooler configured to cool the 2in1 power modules; a capacitor facing a first rectangular side of each 2in1 power module, and having a vertical front surface facing the cooler and 2in1 power modules, a vertical rear surface, a left-hand side vertical surface comprising terminals for connection to DC bus-bars, and a right-hand side vertical surface parallel to the left-hand side vertical surface; an L-shaped positive DC bus bar connected to the 2in1 power modules, the positive DC bus bar having an electric power terminal for connection to the capacitor; an L-shaped negative DC bus bar connected to the 2in1 power modules, the negative DC bus bar having an electric power terminal for connection to the capacitor; respective control signal wires connected to the 2in1 power modules; and respective drive circuit boards, located on a same plane, and configured to deliver control signals to the control signal wires; wherein the 2in1 power modules are mounted to the cooler along a vertical direction that is also a long-side direction of the 2in1 power modules; the power conversion device further comprises: plural AC bus bars respectively connected to the 2in1 power modules, each AC bus bar having an output terminal, each AC bus bar extending horizontally parallel to each other on the same plane parallel to the surface of the cooler; the L-shaped positive DC bus bar and L-shaped negative DC bus bar respectively having vertical front portions parallel to the cooler for electrical connection to the power modules and located between the vertical front surface of the capacitor and the AC bus bars and side vertical portions perpendicular to the cooler, the side vertical portions extending parallel to the left-hand side vertical surface of the capacitor, and the side vertical portions respectively containing the electric power terminals for connection to the capacitor; and wherein connections of the control signal wires to the respective drive circuit boards together with the drive circuit boards face the right-hand side vertical surface of the capacitor; and wherein a center line, perpendicular to the vertical direction and the cooler, of the capacitor is located on an upper side of a center line, perpendicular to the vertical direction and the cooler, of the drive circuit boards.