PURPOSE: To improve reliability by executing information processing with a redundant system information processor in parallel with a main system information processor and continuing the information processing without being interrupted when the main system information processor is in fault.

CONSTITUTION: A main system information processor 2 and redundant system information processors 3a and 3b, which execute the information processing in parallel with the main system information processor 2, input various sensor information on a bidirectional data bus 1 through data communication circuits 4a and 4b, execute the information processing by information processing circuits 5a and 5b and output processed results through the data communication lines 4a and 4b to the bidirectional data bus 1. At this time, since it is controlled by fault detection circuits 14a and 14b to output the data only from the normal system, even when that the main system information processor 2 breaks down, the information processing can be continued without being interrupted by switching the input/output to the redundant system information processors 3a and 3b which execute the same processing in parallel. Thus, the high reliability can be obtained.