PURPOSE: To consecutively realize the quick restoration of a fault without stopping the fault monitoring processing of a communication control module in a system.

CONSTITUTION: Plural communication control modules 14, 15 consider a system monitor module 13 to be faulty unless a fault monitor information signal from the system monitor module 13 is received within a definite period of time, and the communication control module 14 (15) having found out first the fault of the system monitor module 13 transmits the fault monitor information signal to the other communication control module 15 (14) at a definte cycle, and executes the fault monitoring processing as acting for the system monitor module 13 until the system monitor module 13 is recovered from the fault.