The polishing process, which is the final process in the manufacturing of precision metal molds, takes a long time and often depends on the experience and specialized skills of skilled workers. Development of a skill-less polishing technology and automation of its process, therefore, has become a requirement. One of the most promising polishing technologies is Field-assisted Fine Finishing (FFF). In FFF, an electric field or a magnetic field is applied to control the behavior of the abrasive grains in the polishing process. Here, a new polishing technology using Electro-rheological Gel (ERG) is proposed. The developed ERG is a functional material the induced shear force of which changes according to the applied electric field intensity. A thin ERG sheet on which abrasive grains are scattered is used as the polishing pad of a rotary polisher. The results showed that the polishing efficiency and attained surface roughness of STAVAX stainless steel can be improved by the ERG pad.