This invention relates to a disk drive and a method of writing data to the disk drive. In a disk drive including a write head, a read head and a positioning unit of a head which includes a write element and a read element, the present invention provides the disk drive with a position error measuring unit for measuring the amount of a position error of the write element and the read element; and a write/read control unit for obtaining an offset amount of the head in accordance with the amount of the position error of the head, setting the offset amount to the positioning unit so as to offset the head, and effecting data write/read operation. When format write operation is executed, only an ID portion is offset in the same direction as the direction of the position error so measured in accordance with the measured amount of the position error, and is written.