PURPOSE: To reduce the influence of external magnetic field and to relieve the load of a magnetic head by setting the magnetizational direction of the initialization of an entire disk or a guard band in the same direction as the direction of the leakage magnetic field of an electromagnetic actuator.

CONSTITUTION: By a magnetic field direction control part, the direction (the arrow B) of the leakage magnetic field from an optical actuator is detected and the direction of the leakage magnetic field (the arrow B) is set in the direction where a magneto-optical disk is initialized. By such a constitution, the direction (the arrow D) of the strength of the magnetic field performing magnetic field inversion recording to a required pit is made to coincide with the direction (the arrow C) of stray magnetic field in the pit. Similarly, the polarization, as well of the guard band GB provided on the boundary of the recording area Rs of the magneto-optical disk is made the polarization N of the same direction as the leakage magnetic field and initialized. Thus, the influence due to the guard band GB of a required recording position is reduced.