A power conversion device includes a case including an upper case and a lower case; an inverter that is accommodated in a first partial case and is fixed to the first partial case, the first partial case being one of the upper case and the lower case; and a capacitor that is connected to the inverter by a positive electrode bus bar and a negative electrode bus bar, the capacitor being disposed in an internal space of a second partial case that is another of the upper case and the lower case. The first partial case includes a fastening portion that extends from an internal space of the first partial case to the internal space of the second partial case. In the internal space of the second partial case, the capacitor is fastened to the fastening portion.