PURPOSE: To improve the tracking accuracy and to make the operation stable against the use of lots of kinds of optical disks by using two light beams at both ends of a multi-beam light head so as to apply tracking.

CONSTITUTION: An optical head 21 radiating plural light beams is used to apply tracking to an optical disk 26 having plural parallel tracks, then a tracking error signal by the light beam at both ends of plural light beams is detected. Then based on the tracking error signal, the angle between a straight line tying plural light beams and a track is varied so as to allow the light beam at both ends to follow a prescribed track. Thus, tracking is applied by using two light beams at both ends to collect the light beam existing inbetween onto a prescribed track and highly accurate tracking is attained.