We propose a new approach to easily creating 3D geometric models. A technique called interactive evolutionary computation (IEC) is introduced to accelerate user's invention and inspiration of new shapes. The proposed IEC-based design system generates aesthetically pleasing shapes through the simulation of natural evolutionary processes. The user only is required to specify his/her subjective preference of each shape generated by the IEC. The system allows even beginners with little knowledge and experiences of the 3D modeling to acquire innovative shapes. Because the system is developed based on a 3D geometric modeler using an implicit surface method, it also provides skilled experts with an advanced modeling interface. The experts can directly modify the internal parameters of the 3D models to make them more elaborate ones. Some experimental results are presented to show the potential of the proposed modeling method.