A power supply module includes a circuit board and a heatsink plate. The circuit board includes a first principal surface, a second principal surface, and side surfaces. Electronic components are mounted on the first principal surface. The heatsink plate includes a plate-shaped body portion that faces the first principal surface, and a plurality of fixing portions that extend at an angle from the body portion to face the side surfaces. The fixing portions are configured to come into contact with the second principal surface to secure the body portion to the circuit board.