An abrasive includes an alumina-based fiber bound by a matrix resin which contains diamond abrasive grains therein, and a diamond abrasive grain layer provided on the surface of the bound fiber. The abrasive is formed into, for example, a flat plate having a thickness in a range of 0.45 to 1.2 mm, and the diamond abrasive grain layer is provided on at least any one of opposite surfaces of the bound fiber. Flat filaments having a ratio of a long axis to a short axis of the cross-sectional shape thereof in a range of 1.3 to 1.8 are used for the alumina-based fiber.
