This chapter proposes a small reaction manipulator for detecting anti-personnel mines. The small reaction manipulator realizes rapid and precise motion control, which are useful for the improvement of sensor head maneuver ability. In particular, ground penetrating radar (GPR) requires precise position control to obtain underground information. In order to realize precise and rapid motion control of a sensor head, it is necessary to restrict oscillations caused by end-effector motion. Such mechanical oscillations are produced by fluctuations of kinetic momentum. In order to reduce oscillations, it is necessary to keep kinetic momentum constant. For this purpose the chapter uses counter weights mounted on a small reaction manipulator. By controlling the counter weights, the small reaction manipulator could precisely position the GPR at high-speed without oscillation. The chapter presents some experimental results from the evaluation of the proposed manipulator.