In a serial bus network, an environment is provided, in which the serial bus is divided to two local buses and a specific terminal connected to one of the local buses can reliably occupy other terminals connected to the other local bus without influence on the terminals connected to the local buses. A specific terminal is connected to a local bus 101, to which an inner portal 3 is connected, and an ID information thereof is preliminarily recorded in a ROM 8. After a power source is turned on, the specific terminal connected to the side of the inner portal 3 is detected according to the ID information from the ROM 8. An ID information of all of nodes connected to a local bus 104, to which an outer portal 4 is connected, is read out and stored in a control portion 5. A bus reset is generated on the local bus 101. In order to give a connection information of the local bus 104, a self-ID packet is generated by the control portion 5 and transmits it through a dedicated PHY 6.