To provide a magnetic grinding technique grinding in a narrow range regardless of a size and the like of a magnetic force generating member constituting a grinding tool.

In this grinding tool, a permanent magnet 4 is held by a concave-shaped holding part 3b on a bottom end of a tool shaft 3a. A cap 5 made of non-magnetic silicone rubber and the like with an opening 5a of a diameter D0 bored on a bottom end is attached, and a magnetic fluid M is selectively adsorbed to a portion of the permanent magnet 4 exposed from the opening 5a. A contact range of a workpiece W and the magnetic fluid M is thereby limited to a range of a narrow diameter D1(D0) regardless of the size and the like of the permanent magnet 4, so as to grind the workpiece W in a narrow range, such as to correct a shape.