A power conversion device in an electric vehicle that uses a short-circuit capacitor and is capable of detecting a short circuit of the capacitor by using a simple structure. The power conversion device includes an inductor connected on a main battery side with a switching member provided between the inductor and a power line. The power line connects a first capacitor and a second capacitor as well as an electric load in parallel. A controller is provided for controlling the on/off of the switching member. The first capacitor and the second capacitor are each a small capacitor configured to be short-circuited upon application of an excess voltage. The power conversion device is provided with a detection member for detecting a short circuit of any one of the first capacitor and the second capacitor. The detection member is connected in series to the first capacitor and the second capacitor.