Abstract: A roll forming method is used for forming an annular product with a radially outwardly extending flange portion at an end and includes steps of holding a center portion of a work for forming the annular product by a holding device, rotating the work, contacting a circumferential end portion of the rotating work with a forming roller to be pressed to form the flange portion while retaining a circumferential outer end of the work. The present invention is advantageous in that the resultant product has a good quality without deficiency, such as underfill of the material and has an improved toughness unlike a cast product, a product made by welding and the like of the same structure.