A power conversion device includes an input conversion module, an output conversion module, a filtering module and a controlling module, which are installed on a main board. The main board includes a first edge, a second edge, a third edge and a fourth edge. The first edge and the second edge are opposed to each other. The third edge and the fourth edge are opposed to each other. A first part of the input conversion module is located near the first edge and the third edge. A second part of the input conversion module is near the first edge and the fourth edge. An airflow channel is formed between the first part and the second part. The output conversion module is near the second edge. The filtering module is near the second edge. The controlling module is arranged between the first part and the third edge.