Three-dimensional models (CAD models) are constructed in the design processes of products because they are effective for design evaluation processes using CAE systems and manufacturing processes using CAM systems. However, mock-ups or prototypes are still required in the evaluation processes of designability and operability of products because the evaluation of the operations of real products is essential. It is however time-consuming and costly to make prototypes or to develop trial products for evaluation. For this problem, considerable studies have been conducted on the use of mixed reality technology by overlaying an image of the design model onto a physical model using a Head-Mounted Display (HMD) to evaluate the designability and operability of a product. Such technology reduces the need for making physical mockups (prototypes and trial products), but HMDs have drawbacks such as causing motion sickness and physical weight, bulkiness of the display, and high costs. In this paper, a method using projectors is proposed to establish mixed reality technology which does not have the drawbacks of HMDs. A mixed reality system was constructed according to the proposed method, and applied for evaluating designability and operability of products without physical mock-ups. In the mixed reality space built by the system, the functions of a product can be held in the hand as if they were real products.