A power conversion apparatus for vehicle use having a small size and a light weight is obtained. The power conversion apparatus is provided with: a plurality of semiconductor modules in which semiconductor devices are molded with a resin, and each of which has a module body, an input terminal, and an output terminal; a heat sink of a rectangular parallelepiped shape which has cooling principal planes on opposite surfaces thereof, respectively, for cooling these semiconductor modules; and a plurality of control boards which control the driving of the semiconductor modules. Each of the semiconductor modules is arranged such that its module body has a principal plane in surface contact with one of the cooling principal planes of the heat sink, and each of the control boards is arranged in opposition to a surface of the module body at an opposed side of the principal plane thereof.