An RW offset setting method which includes recording a test pattern by a write head, reading the test pattern by a read head, measuring an amplitude of a read back signal at each tracking position, finding an approximate expression of a profile of the measured amplitude, finding a tracking position, and finding a RW offset based on this tracking position, setting a RW offset for all tracks in the disk device based on the RW offsets about the plurality of tracks to be measured. A read data error recovery method that includes the steps of determining an off-track direction where the amplitude increases, searching an off-track position where the amplitude becomes a local maximum, measuring the amplitude at each off-track position reading data recorded in the data sector.