An alternating magnetic field assisted finishing (MAF) technique has been developed to finish the 5–20 μm wide pore sidewalls of micropore X-ray focusing optics fabricated using microelectromechanical systems (MEMS) techniques. To understand the material removal mechanism, this MAF technique is used to finish a silicon MEMS micropore X-ray optic that had previously undergone a hydrogen annealing treatment. Compared to the unfinished surface, distinctive surface features are observed on the finished surfaces using scanning electron microscopy, optical profilometry, and atomic force microscopy (AFM). This demonstrates the finishing characteristics and reveals material removal on the nanometer scale. Moreover, the representative unfinished and finished micropore sidewall surfaces show a reduction in roughness due to finishing from 1.72 to 0.18 nm Rq.