We are developing a breadboard model of a wireless power transmission (WPT) experiment using a small scientific satellite toward a solar power satellite (SPS). The breadboard model can steer the microwave beam of the 5GHz band by the software retro-directive method using the pilot signal of the 1GHz band. We carried out the fundamental beam control experiments using the bread board model that had multiple pilot signal receiving systems. Preliminary results on the beam directional control accuracy were described.