PURPOSE: To find out a fault and to confirm computer processing by generating a unique and different value from each process as a simulated process data.

CONSTITUTION: A process communication data simulator 6 started via the operator console fetches a simulated data generation parameter set by the operator simultaneously. Then a reference data generating section 17 is started, a generation reference data is generated based on the said parameter and stored in a generation reference data table 16. Then a process data generating section 15 is started to generate a simulated data based on the table 16 and a data transmission section 14 sends the generated data to a data reception section (not shown) via a communication controller 3. Thus, the discovery of a fault and the confirmation of the computing processing are attained.