Recently haptic shape modeling has got a momentum in industrial and conceptual design. In this paper, a real-time haptic interface of synthesized shape modeling and haptic function evaluation of product design for multi-material part is presented. Due to the advancement of manufacturing technologies, multi-material is increasingly employed by industrial designers as a means for increasing the appeals of a product while also adding functional capability. Multi-material part manufacturing processes allow designers to select different materials for different portions of a product in order to improve the material-function compatibility for the overall product. For quick design verification, the shape design and function evaluation are implemented in the same haptic environment where a load can be applied to a part design using a haptic device and at the same time the combined reaction of the part in terms of displacement and reaction can be visualized and felt by the user. The intuitive correlation between the applied force and incurred displacement (or deflection) provides an instant evaluation of the stiffness of a part design. The proposed methodology is illustrated through a case study: the design of a toothbrush.