Considering that there is no pump feeding an Electro-Rheological-Fluid, a new type of pump has been manufactured and fluid dynamic characteristics have been elucidated. This pump can feed the ERF by utilizing effectively the change in physical properties of the fluid by the application of voltage. The principle and configuration of this pump and the methods of theoretical analysis are described, and the influence of the voltage on the feeding characteristics was examined The dispersoidal ERF has been treated hitherto as a type of Newtonian fluid. However. experiments showed that not only the induced shear stress but also the viscosity is affected by the electric field strength and that the ERF must be treated as a pseudo-plastic flow. The method of analysis described here can be applied to design the pump differing in dimensions because the analysis gave qualitative evaluations about the flow rate and pressure difference.