An assistance device of workpiece inspection apparatus embodying this invention includes a regional image data conversion unit which inputs region data indicative of a specified region of a workpiece being tested with a pattern formed thereon, and then converts the data to regional image data. The device also includes a data distribution processing unit which distributes the regional image data for output to the workpiece inspection apparatus in conformity with an inspection processing speed of the external workpiece inspection apparatus, which performs pattern defect inspection while comparing optical image data of the workpiece to prespecified reference image data.