Recently, real-world haptics has been researched for tele-operation system. Conventional bilateral control can achieved corresponding master and slave position and action-reaction law. However, if system has flexible mechanism, performance of conventional bilateral control is degraded. Firstly, vibration occurs at slave load side by its flexibility. Secondly, an error between motor position and position of load occurs and synchronism position is not achieved. Thirdly, action-reaction law is not realized as well as position error. In this paper, the structure of bilateral force feedback control in the case of the slave system including the flexibility is proposed. Therefore, the proposed control structure has three important components in the slave system. Firstly, in order to suppress the vibration, resonant ratio control is implemented. Secondly, for corresponding to master and slave position, a modified control goal which is added reaction force estimated by load disturbance observer is proposed. Moreover, action-reaction law between master and slave load is accomplished by positive feedback of load reaction force multiplied inverse system. The effectiveness of the proposed method is verified by actual experiment.