To easily perform magnetization on the magnetization surface of a core material and the release while concentrating magnetic lines on the magnetic part of the core material by a cylindrical magnet and generating strong magnetism.

The core material 3 having a nonmagnetic part 3B and the magnetic part 3A with the magnetization surface 3a is inserted so as to be freely relatively moved in an axial center direction into the cylindrical magnet 2 having a magnetic vector in a direction orthogonal to a cylindrical center, and the nonmagnetic part 3B and magnetic part 3A of the core material 3 facing the magnet 2 are changed by the relative movement.