The modeling and formulation of simultaneous optimization problems with mixed 〓2/〓∞ norm objective function are discussed in the paper. They are applied to the simultaneous optimization of the cross-sectional parameters of a spring-supported beam and the parameters of the controller used to actively suppress the vibration of the beam. The weighted sum of 〓2 and 〓∞ norms of the transfer functions from external disturbance to measured outputs is used as the objective function. Simulataneous optimization is realized by iteratively executing structural optimization and controller optimization. Both serial and parallel approaches to combine structural optimization and controller optimization are investigated. The performance of both output and control input is improved significantly after simultaneous optimization. The simulation results show the great potential advantages of simulataneous optimization over tranditional design methods.