PURPOSE: To enable it to grind a flat surface and a complex curved surface irrespective of size of a workpiece and not limiting the working surface to a cylindrical surface by holding magnetic abrasive grains on the outer circumferential surface of a disk with magnetic force, and grinding a surface of the workpiece with these magnetic abrasive grains rotating together with the disk.

CONSTITUTION: When a nonconductive material-make disk 3 is set to a spindle 1 of a machine tool and an electromagnet 4 is excited, both N and S poles are alternately produced in the circumferential direction of an outer circumferential surface of this disk 3 so that a line of magnetic force is generated in space between these poles. Next, when magnetic abrasive grains MB are fed to this part, these grains MB are held around the disk 3 by dint of magnetic force. If the spindle 1 is rotated in this state, the magnetic abrasive grains MB kept on the outer circumferential surface of the disk 3 rotate together with the disk 3, whereby the grains MB with this rotational speed comes into contact with a workpiece W and grind the surface.