This paper introduces a sensor-less grasping control technique on two-finger robot hands with visual feedback control. A great number of robot hands have been developed and most of the hands mount many kind of sensors, such as rotary encoders, tactile sensors, and force sensors. However, use of the many sensors increase the cost of robot hands and decrease the reliance. On the other hand, when we observe and assemble some object carefully, we gaze at it but not watch our fingers. Thenfore, as an analogy, robot hands for observationa or assembling may not always need the jount angle sennsors if the system has some vision sensor. Meanwhile, Shimada et.al. have presented an unique sensorless control technique for electric motor driven mechanical systems. It is useful and easy to install but it has been developed only for single digree of freedom systems. Then, we try to extend the sensorless control technique to practical multi-finger robot hand systems with some vision systems. This paper describes the basic technique and show some simulation results for evaluation of validity.