A power conversion device includes a main board, a connector module, an input conversion module, a capacitor, an output conversion module, a control module and a conducting part. The main board includes two lateral edges along a first direction and two lateral edges along a second direction. The connector module is mounted on the main board, and includes an input connector and an output connector. The output connector is located under the input connector. The input conversion module, the output conversion module and the control module are perpendicularly mounted on the main board. The conducting part is in parallel with the control module and electrically coupled with the input connector or the output connector. The connector module, the input conversion module, the capacitor and the output conversion module are mounted on the main board and arranged in a line along the second direction.