A signal line, a power supply pattern and a ground layer are formed within a board. An outer via and an inner via are formed within the board. The outer via is connected to the signal line. The inner via is connected to the ground layer. The outer via serves as a signal line. The inner via serves as a ground. The signal line within a printed wiring board is connected to the outer via without interruption by a ground. The signal lines can spread within the printed wiring board in a complicated pattern as compared with a conventional pattern. Moreover, the impedance matching can reliably be established.