Provided is a printed circuit board (1) on which the power supply circuit is mounted and a casing (2) which is shaped like a flat as a whole and in which the printed circuit board (1) is housed. An input terminal (11) of the power supply circuit is connected to an input socket (3) fixed to one end part, in a direction perpendicular to a thickness direction of the printed circuit board (1), of the casing. An output terminal (12) of the power supply circuit is connected to an output socket (4) protrudes from one side, in the thickness direction of the printed circuit board (1), of the casing (2). The casing (2) has a bulge part (21) which protruded to an opposite side to the protruding side of the output socket (5) and to which the input socket (3) is fixed.