Magnetorheological Fluid (MRF) is a functional fluid in which apparent viscosity changes quickly, continuously and reversibly according to the strength of the magnetic field applied. On the basis of the peculiar features of MRFs various studies have been conducted mainly on functional fluids in the power fluid field. MRF consists of magnetic substances of the size 1-10 μm which are dispersed in lubrication oil having low viscosity and specific gravity. There is no MRF which can be used in robots for precise control because it cannot guarantee the reliability. We here aim to acquire advanced robot mechanism by fusing material-mechanical technology and crossing hypothesis-experiment cycle. As a result, we found that anti-sedimentation of MRF can be regarded as the most important features for implementation in robotic mechanisms. In this paper, the anti-sedimentation MRF is manufactured and tested in a MRF damper. We first obtained a common method to manufacture the anti-sedimentation MR fluid, by designing the medium, the magnetic substance, and the additive. In the sedimentation test, the proposed MR fluid had the minimum separation compared to the commercial product. Secondly, in experiment using the MR damper, the anti-sedimentation MRF had superior stability compared to the commercial product.