A tracking servo apparatus for controlling a position of a light beam to follow an information track on an information storage disk. In response to a drive signal, a light-deflection mechanism moves the light beam onto the disk transversely with respect to the information track. The photodetector detects the difference in the intensity of the light beam in half sections and produces a radial error signal. The radial error signal is corrected in response to the drive signal which is applied to the light-deflection mechanism, and then a new drive signal is produced depending upon the corrected radial error signal.