iArmS is an Auto-adjusting arm holding robot to provide stable operation quality by supporting the surgeon’s arms. In long operation time, the surgeon’s arms are so fatigued that they could be trembling. iArmS serves as assistive device to reduce the fatigue and trembling of the arm and improve the operation accuracy. Operating table placed at the arm end detects the subtle force applied to the arms by surgeon and conducts automatic adjusting and stop. With this robot, the surgeon can concentrate on the operation with the support as if his intensions are understood.