A search range for detecting the peak position of an envelope on a rotating magnetic recording medium is limited to a predetermined range on either side of an absolute track position of each track on the recording medium. A limitation is also placed upon the number of times a magnetic head is fed within this predetermined range. If a peak cannot be decided even when the magnetic head is fed the limited number of times, the final position of the magnetic head is adopted compulsorily as the peak position. As a result it is possible to reduce the time needed for peak position detection processing. When an envelope cannot be detected with the predetermined range, the absolute track position is adopted as the peak position.