<p>SUS304 is one of the high-value and widely used materials in many different industries. However, SUS304 is categorized as a difficult to machine material, so traditional machining methods for processing SUS304 material take a lot of time and their effectiveness is reduced. This issue can also have an impact on economic factors. In this study, we will first clarify the formation process of a polishing tool using magnetic abrasive fluid (MAF) under the influence of a rotating magnetic field. Then, the impact of eccentric distance, the method of applying the magnetic field to the geometric shape, as well as the repetition cycle of the MAF mixture's shape will be analyzed for the polishing process, and this will also be presented in this study. The author has proposed a polishing process to create a high quality and efficient surface of SUS304. The surface roughness obtained in the nanoscale range is not damaged after processing by the magnetic polishing process. Surface roughness is systematically analyzed through the influence of factors MAF cage velocity, workpiece velocity, magnet disc velocity as well as machining distance. The surface state analysis results show that the polishing ability applies to SUS304 material. From many experiments, the results show that after 90 mins of machining, an ultra-fine SUS304 surface is formed with a surface roughness of Ra = 2.533 (nm). Polishing by MAF under rotating magnetic field shows the potential of an advanced technique to improve surface quality not only for SUS304 but also for other difficult to machine materials.</p>