Recently, as CAD systems have spread, style design with digital mockups has been used. But physical mockups are still used to evaluate the ergonomic design of products. However, the conventional methods of the evaluation using a physical mockup of a product are inefficient in an upstream style design process, for it takes time and money. So, our research purpose is to develop a system for ergonomics design, which enables ergonomic assessment for a handheld information appliance without “real” subjects and physical mockups by integrating a digital hand with a product model and its task operation model.