PURPOSE: To provide a low priced and efficient electrorheological fluid having, in one side, high electric activity and low electric conductivity in a needed industrially appropriate temperature range that is below 140°C and, in the other side, good dispersion stability and low abrasiveness.

CONSTITUTION: The electrorheological fluid consisting of a metallic silicate hydrate which does not contain aluminum having substantially a sheet structure, a dispersion promoter and an inert aprotic dispersion medium, is developed. The metallic silicate hydrate is preferably a type of kenyaite, magadiite and/or kanemite. The dispersion medium is preferably a silicone oil having a viscosity range of 0.5-1,000 mPas and/or a mineral oil or paraffinic oil having a viscosity range of 0.1-1,000 mPas. The metallic silicate hydrate is added to the electrorheological fluid with a concentration of 1-50 wt.%.