After component design using a 3D-CAD system and a product model, if the result of the design checking system is violated, it is necessary to re-design until it is satisfied. Since this increases the number of data transferring, the improvement of efficiency is desired. Thus, in this research, we have developed MultiAgent-CAD to support the user's design by providing a multi-agent system including simplified code checking agents, external condition checking agents, etc., using the function of interoperability by the product model. Further, we have developed a 3D product model of steel structures and applied the MultiAgent-CAD to a sample design case to demonstrate its effectiveness.