Provided is an in-vehicle power conversion device in which a smoothing capacitor includes a first electrical connection portion, a second electrical connection portion, a mechanical connection portion, and a smoothing capacitor main body. The first electrical connection portion is electrically connected to a first conductor. The second electrical connection portion is electrically connected to a second conductor. The mechanical connection portion functions as an additional electrical connection portion configured to fix the smoothing capacitor main body to the first conductor or the second conductor to be electrically connected to a fixing destination of the smoothing capacitor main body.