An electronic control unit includes a board, an electronic device, a heatsink, and a fastener. The board includes a protection layer and a ground pattern covered with the protection layer. The ground pattern has an exposed portion exposed outside the protection layer. The electronic device is mounted on the board and has an anode terminal and a cathode terminal connected to the ground pattern. The heatsink supports the board. The fastener is inserted though an insertion hole of the exposed portion. The fastener electrically connects the ground pattern to the heatsink and fixes the board to the heatsink. The exposed portion is located on the cathode terminal side of the electronic device.