For fluid-driven micromachines carrying out power-needing tasks such as maintenance in a limited space, a valve-integrated microactuator using a homogeneous electro-rheologi- cal (ER) fluid is proposed and developed. A valve using a homogeneous ER fluid whose viscosity is controlled by means of the applied electric field strength, termed the ER valve, consists of fixed electrodes and features a miniaturizable simple structure with high reliability. First, in this study, to realize high performance of the micro-ER valve fabricated by micromachining, the static and dynamic characteristics of the micro-ER valve with different nematic liquid crystals, bend numbers and electrode gap lengths are experimentally investigated. Second, a polyimide-diaphragm fluid microactuator whose structure is simple and without sliding parts is proposed, fabricated and tested. Third, an ER valve-integrated microactuator combining the fabricated 3-port micro-ER valve and a polyimide-diaphragm fluid microactuator is constructed with an effective size of 8.0101.4 mm3 and its characteristics are experimentally examined. Finally, a microgripper driven by the ER valve-integrated microactuator is fabricated and the drive is attempted.