The current status of research and development of an electrodynamic tether (EDT) system for space debris mitigation is described. EDT is a kind of advanced propulsion technologies, which requires no propellant and electric power in theory. Since debris de-orbit systems need highly efficient propulsion systems, EDT can be one of the most attractive candidates. The first step to make the debris removal system practical in future is the demonstration of the EDT operation on orbit because no one has ever demonstrated the thrust generation by EDT. Therefore, we have been conducting research and development of an EDT system using a small satellite. In this paper, the concept of the EDT demonstration on orbit and the current status of the research and development are described.