This paper describes an ultraprecision polishing method of larger scale X-ray mirrors which made of fused silica, and the polishing characteristics. The X-ray mirrors which ground high form accuracy with ELID-grinding used #4000 cast iron bonded diamond wheel, it was took polishing with NC control polishing machine using a small polishing tool and Ce_2O_3 slurry. In the results, very good ground surface of Ra < 1nm mirror can be achieved.
