A smart structure is composed of the piezoelectric film sensors and actuators in order to reduce the structural vibration. H_2 controller is designed with the reduced order model of the smart structure which is obtained by finite element and modal analyses. The control force is applied by the piezoelectric film actuator and the feedback signals are detected by the piezoelectric film sensor and the accelerometers in the system. The vibration response is suppressed by the modal control and the displacement control in which the shape of the piezoelectric actuator is appropriately designed for the enhanced control performance. Efficient optimization algorithm based on a two-step procedure is employed in the simultaneous optimization of piezoelectric shape and H_2 control system. It is verified by some applications that the enhanced performance for the vibration suppression can be achieved by the presented optimum design.