An magneto-optical disk drive comprises a driving apparatus for rotating a medium, an electromagnet positioned above or below the medium for producing a magnetic field on a recording surface of the medium, and an optical head by which laser light illuminates the recording surface and the laser light reflected from the recording surface is picked up. Here, the electromagnet comprises a plurality of subdivided electromagnet elements, a magnetic field concentrator by combining the electromagnet elements in a magnetic circuit and concentrating magnetic fields produced from the combined electromagnet elements on a portion of the electromagnet, and a center magnetic pole provided in an opposing position with respect to the optical head, to thereby make the magnetic field concentrated by the magnetic field concentrator pass through the recording surface of the medium. Accordingly, the recording time or data on the medium becomes greatly shortened, thereby enabling high speed data recording.