A multi-layered printed wiring board, capable of securing required wiring density even with a decreased number of wiring layers and reducing radiation noises, has at least three wiring layers each at least having at least one power supply line or a ground line, and another kind of line, the wiring layers each having an outer edge. A ground line is formed at the outer edge of at least one of the wiring layers. A basic power supply line is formed inside the ground line. At least one power supply line extends from the basic power supply line. A plurality of electronic parts are mounted on at least one of the wiring layers. The at least one power supply line is wired to mounting positions of the electronic parts via at least one of the wiring layers.