PURPOSE: To execute efficient writing of data and to improve a processing speed by subjecting only the track where abnormality is detected in data to rewriting of the data.

CONSTITUTION: This device is provided with writing magnetic heads a1 to a4 constituting a writing-only head and reading magnetic heads b1 to b4 constituting a reading-only head. Only the defective track is subjected to rewriting by the writing magnetic head corresponding to the defective track if the presence of the defective track is found by a verifying check after writing of the data. Rereading of the rewritten data from only the defective track is executed by the reading magnetic head corresponding to the defective track parallel therewith, by which the verifying check is made. As a result, the rewriting of only the defective track is executed. Rewriting is not executed by holding the track once normally written with the data intact and, therefore, the fresh generation of the writing defect by movement of dust, etc., is obviated and the efficient writing of the data is executed. The processing speed is thus improved.