To provide a demagnetization method and a demagnetization apparatus capable of reducing processing time while reducing a highest required magnetic field for demagnetization and demagnetization magnetic field intensity, and in addition, capable of demagnetizing, without disassembly of rare earth magnet built-in device, a rare earth magnet of its inside.

The demagnetization method includes steps of: applying a pulse magnetic field in a direction perpendicular to a magnet orientation direction of a magnet to be demagnetized; and next, demagnetizing by applying an alternating attenuation magnetic field in the direction perpendicular to the magnet orientation direction. The pulse magnetic field may be applied alternately in normal and reverse directions. It is preferable that the alternating attenuation magnetic field weaker than the pulse magnetic field is applied.