To enable generating a magnetic field varying a direction and magnitude of the magnetic field by a single phase AC power source.

A magnetizer comprises a first exciting coil 5 in which one pair of coils 3, 4 wound on magnetic poles 2a, 2b of both opposed ends of a yoke 2 are connected in series and both ends of the coil are connected to an AC power source AC, and a second exciting coil 8 in which one pair of coils 6, 7 wound on the magnetic poles 2a, 2b in parallel with each coil 3, 4 of the exciting coil 5 respectively are connected in series and both ends of the coil are connected to a capacitor C. And magnitude and a direction of a magnetic field generated between the magnetic poles 2a and 2b can be varied by leading a current flowing in the second exciting coil 8 for the current flowing in the first exciting coil 5.