The sector synchronism of a timing generation section for generating data recording/reproducing timing is corrected at the address-mark detection timing of an address-mark detection section. Moreover, even if only one piece of address information having no error is not reproduced in the sector concerned, when at least one piece of address information having no error is reproduced in any of a predetermined number of sectors preceding the subject sector and at least one address mark is detected in the subject sector, the data recording/reproducing is permitted, and thus, the data is recorded/reproduced at a high speed and a high reliability even if an error rate of a physical address is deteriorated.