A　disturbance　observer-based　control　scheme　is　proposed　for　free-floating　space　manipulator　with　nonlinear　dynamics　derived　using　the　virtual　manipulator　approach.　The　derived　dynamic　equation　uses　only　link　angles　as　generalized　coordinates,　which　is　suitable　for　the　controller　design　in　joint　space.　Since　joint　coupling,　model　uncertainties　in　robot　dynamics　are　treated　as　lumped　disturbances,　a　disturbance　observer　is　developed　at　each　joint　of　degree-of-freedom　space　manipulator　to　decouple　and　simplify　the　controller　design.　Simulation　results　of　a　six-link　space　manipulator　show　that　the　proposed　scheme　achieves　superior　performance,　especially　when　large　external　disturbances　are　present.