An optical head which can be rotated about the rotation center by a magnetic force. There is a photodetector which is divided into a plurality of detection regions and as the optical head rotates, different detection regions are examined to determine a tracking error. Rotating between the inner and outer peripheral portions of an optical disk, the optical head selects a track on the optical disk on which information is recorded, radiates a light beam focused on the selected track, receives the light beam reflected by the optical disk to a second photodetector having three divided parallel sensor segments, and reproduces the information recorded on the optical disk. In consideration of the fact that in an optical disk rotated at a constant angular velocity, the degree of modulation of a retrieving information signal recorded on a recording layer on the optical disk is increased toward the outer peripheral portion, the sensor segments of the photodetector are arranged such that the projection of a track on the inner peripheral portion in an information recording area, of track projections which move on the sensor segments, does not cross the three divided sensor segments upon rotation of the optical head.