In this study, both mechanical and electrical fatigue properties of electrorheological (ER) materials whose global characteristics can be controlled by an external electric field are experimentally evaluated. In order to investigate the mechanical fatigue property, a linear reciprocating apparatus is devised and operated by the hydraulic unit. Two important characteristics of methylcellulose based ER material: the field-dependent yield stress and current density are investigated as a function of the operating cycle. The electrical fatigue property is investigated by applying high voltage to the ER material domain through the electrode gap. The voltage is imposed in on-off manner for the specific cycles by changing the field intensity. The yield stress and current density of the ER material are evaluated at each specified cycle and surface roughness of the electrode is observed as well.