PURPOSE: To positively generate program malfunction caused by the error of program occupation control at a close coupled multiprocessor system composed of virtual processors.

CONSTITUTION: A priviledge instruction communication part 8 for virtual computer registers a processor occupation control instruction and a processor occupation control cancel instruction on a real processor 1 as priviledge instructions for virtual computer. A processor occupation control part 6 simulates the processor occupation control instruction and the processor occupation control cancel instruction, and a virtual computer schedule part 7 switches virtual computers 4-1 and 4-2 in a short time by setting a virtual computer timer value to a virtual computer timer setting part 11 so that one time of real processor time applied to the virtual computers 4-1 and 4-2 in a processor occupation control block can be short in comparison with the processor occupation control block.