PURPOSE: To reduce the repetition of debugging, by providing a correction management memory, where the log of corrections is stored, while facilitate the respons to a source list.

CONSTITUTION: Contents of a program PRG incorporated in a device 36 to be tested are fetched into a RAM32 for emulation through an externak interface circuit. After that, the device 36 is operated by the PRG stored in the RAM32. In this case, a command signal is inputted from a keyboard 30 to operate the device 36 in every several steps. In respect to the operation defect in this operation, the PRG is corrected manually from the keyboard 30. A PRG list for correction is displayed on a CRT35 by a controller 31. Consequently, the operator corrects the PRG while watching the PRG sequence displayed on the CRT35. At this time, the controller 31 stores corrected addresses of the PRG in a correction management memory 33.