To make handleable a computer system similarly to a single ring- shaped communication path in which first and second computers have a communication processing part one by one by operating the communication processing part except for a specified communication processing part like the passing point of communication data.

When transmitting communication data from a computer 1a to a computer 1e, the communication data are transmitted in the order of communication processing parts 2a-1, 2b-1, 2d-1, 2c-1, 2b-2 and 2e-1. The communication 1b is provided with communication processing parts 2b-1 and 2b-2, the communication data passing through a ring-shaped communication path 4b twice pass the computer 1b and it seems two computers 1b are connected. Then, the communication processing part 2b-2 does not communicate with a processor part 3 but transmits data received from the adjacent communication processing part 2c-1 to the next communication processing part 2e-1 as they are. When any fault occurs in the communication processing part 2b-1 and the communication with the processor part 3 is disabled, the roles of the communication processing parts 2b-1 and 2b-2 can be exchanged.