PURPOSE: To impart a magnetic field that is most suitable for recording and erasing onto a light spot without enhancing the accuracy of a fitting position of a magnetic head by performing the recording in advance with individual heads of plural magnetic heads and making a magnetic head with which a regenerative signal level becomes the max. a regular recording and erasing magnetic head.
CONSTITUTION: Plural magnetic field modulating magnetic heads 13-15 are arranged to be fixed onto a floating slider 4 so as to coincide with a position adjacent to the light spot. Then, at the stage of an initial operation of the device, the recording is performed in advance by using the magnetic heads 13-15 respectively, whereas a means is provided to select a magnetic head with which its regenerative signal level is the max. As the regular recording and erasing magnetic head. By this method, without enhancing the accuracy of the fitting position of the magnetic head corresponding to the light spot 10, the optimum recording and erasing magnetic field can be imparted onto the light spot.