Actual bladed disks with small variations are called mistuned systems. Many researchers suggest that mistuning, although negatively affecting the forced response, has a beneficial (stabilizing) effect on blade flutter (self-excited vibration). Therefore, in blade design, a bladed disk must be optimized for forced vibration and blade flutter. We proposed a simultaneous optimization method of bladed disks for forced and self-excited vibration, considering the amount of unbalance that causes rotor vibration. This method uses alternate mistuning to suppress the blade flutter. We measured the natural frequency and weight of all the blades of a disk, as in the traditional development process. Then, we assembled a mistuned system retaining the alternate mistuning, and generated analysis models based on the measured natural frequencies and weights of the blades. Finally, we analyzed the resonant stress and the amount of unbalance in the mistuned system repeatedly, sorting the blades and retaining the alternate mistuning of the disk. The simultaneous optimal solution was explored by MCS or DDE (Genetic algorithm). To reduce the computational time, we used the reduced order model FMM to calculate the resonant stress and the stability of the mistuned bladed disks. Further, we verified the validity of the proposed method by applying it to a mistuned bladed disk of a steam turbine.