The master-slave system is expected to be a key technology for the next generation of robots. Indeed, in many fields of operation, a master-slave system is needed to remotely perform tasks in unknown environments. However, in past researches, master-slave systems consisted of the ground based devices with limited workspaces. In this paper, the teleoperation system consists of a 3 DOF haptic device and a two-wheel driven mobile manipulator. In this system, the working areas of these robots are different. To realize the expansion of the working area of this system, in this paper, a master-slave control by force feedback based virtual impedance controller with scaling ratio and the algorithm extending the working area of the slave robot were proposed. In this paper, the effect of the scaling ratio in the master-slave controller is analyzed by using 'Reproducibility' and 'Operationality'. Furthermore, experimental results show the efficiency of the proposed method.