Electro-Rheological Fluids (ERFs) are functional fluids that change their apparent viscosity by applying electric field. ERF is composed of ER particles and silicon oil. ERF shows reversibility and high responsiveness of ER effects, but has a defect that passage of time causes sedimentation of ER particles. Electro-Rheological Gel (ERG) has been developed to overcome the defect of ERF. ERG is composed of ER particles and silicon gel. A flat plate placed on the ERG sheet clings to the gel by applying an electric field and ERG produces the shear force to the plate. The one-sided pattern of electrodes, which has been developed for ERF devices, is a very useful idea to free sliding or rotating parts from wiring arrangements. In this study, the optimum design of one-sided pattern electrodes for ERG is carried out by means of a numerical analysis. The general-purpose tool for the analysis of electric and magnetic field 'ANSYS Emag' is used. The influences of the electrodes pattern on the performances of ERG are analyzed and the yield forces are estimated from electric field intensity at the interface between the electrodes and ERG. Some experiments are also carried out to examine the validity of the numerical analysis.