An approach for integrated optimum design of structure and control system is presented based on modal analysis. This approach consists of two process, namely the process by sensitivity analysis using optimal regulator theory and the process by the complex method in which a control system is composed of a small-order output feedback. In both processes, the design variables of the structural and the control parameters are optimized simultaneously in order to minimize the response due to disturbances of both white noise and colored noise. The integrated optimum design is performed by minimizing the objective function with respect to the response under the constraints of the control cost and the stability of the closed-loop system corresponding to high order natural modes. The validity and the usefulness of the present approach are verified by a vibration control experiment with a steel plate.