A composite flexible wiring board comprises a first flexible wiring board and a second flexible wiring board on which a surface-mounted part is provided. The second flexible wiring board is disposed on the first flexible wiring board in its predetermined area. The first flexible wiring board and the second flexible wiring board are electrically connected to each other through an interlayer contact portion provided in a predetermined position. The first flexible wiring board has an input terminal region and an output terminal region with a power IC chip mounted on the first flexible wiring board.