To collect the fault information centering around the data of higher priorities and also to collect the representative data of lower priorities hen plural faults simultaneously occur by locking the fault information which cannot be updated if the fault occurs while another fault is processed.

An input/output processor 5 notifies a central processor 3 of a fault occurring at a channel part 6a and also locks a fault information saving area 2 to prepare to transfer the fault information data. Then a fault information control part recognizes that the transfer of the fault information data is prepared. Meanwhile, if the fault information control part recognizes a fault of a channel part 6b, the fault of the part 6b is informed to the processor 5. When the processor 5 notifies the processor 3 of the fault of the channel 6b, the fault information control part acquires a lock flag and inhibits writing to a fault information data part while the lock flag is acquired.