PURPOSE: To realize a function detecting the internal fault without damaging the processing ability of a processor by using a general processor.

CONSTITUTION: A basic processor 21 performs the normal information processing, and a redundant processor 22 having the same function as a basic processor 21 performs the same information processing to the basic processor 21 delayed by one cycle. A comparator 1 constituting three-staged pipe line draws all the input/output signals of the basic processor 21, and draws the output signal of the redundant processor 22 as soon as a two-staged redundant processor interface part 12 outputs the input signal of the basic processor 21 to the redundant processor 22. A three-staged output signal comparison part 13 compares the output signal of the basic processor 21 with the output signal of the redundant processor 22 to detect the internal fault.