To provide a cutter capable of stably reducing vibration over a range from low-speed to high-speed rotation.

The cutter includes a chuck table for supporting a workpiece and a cutting blade for cutting the workpiece supported on the chuck table. A rotation balancer is formed on at least one of a fixed flange fixed to a spindle and a fixed nut for fixing the cutting blade to the spindle. The rotation balancer comprises an annular permanent magnet for constituting an inner peripheral wall close to a rotation axis center, an annular chamber defined by the annular permanent magnet and an outer peripheral wall separate from the rotation axis center, and a plurality of ferromagnetic pellets provided in the annular chamber.