This paper proposes a new approach to structuring a free space model in tele-robotic environment by using a slave manipulator equipped with a stereo vision tele-operated by a human operator. Using initial tele-operaeted motion data of the manipulator, structure of the empty space is reliably and conservatively obtained without explicit geometric model of objects in the environment. A post-processing method enables efficient acquisition of the free space model, which is then utilized to autonomously plan collision-free motion. Thus on-line transition to autonomous tele-operation from master-slave manipulation is achieved. This feature enables wider application of the tele-robotic system in unstructured environment.