PURPOSE: To initialize only the region where recording is executed and to increase writing power by adding an initializing magnetic field of the magnitude to the extent of a track width only to the track to be recorded just before recording.

CONSTITUTION: An electromagnet which is an initializing magnetic field impressing means is on-off controlled according to the control of the initializing magnetic field control means 10 in such a manner that only the recording region of a disk where recording is going to be executed is initialized. The medium region initialized in such a manner passes a position to be irradiated with a beam as the disk is rotated by a rotating the laser beam to be irradiated is demodulated according to the information to be recorded by a pulse demodulating means 6. The beam emitted from a laser beam source 7 is reflected by a beam splitter 8 and the initialized part of the medium under impression of a recording magnetic field Hb is irradiated with this beam. As a result, recording is completed.