PURPOSE: To effect the focusing and tracking adjustment thereby to simplify the construction and reduce the size of a drive mechanism and to reduce the power consumption.

CONSTITUTION: A laser beam from its light source 1 is divided by a diffraction grating 8 into diffracted lights of 0, 1 and -1 orders and then is polarized by a polarizing prism 2' and a λ/4 plate 9. The lights thus polarized are condensed as reading and tracking spots upon a video disc 6' through a relay lens 3' and an objective lens 5'. The light reflected on the disc surface 6' is reflected by the prism 2' and fed to light receivers 7' and 7" so that the diffracted components of 1 and -1 orders are fed to a differential amplifier 10 by the receiver 7' whereas the diffracted component of 0 order is fed to a differential amplifier 11 through four light receiving areas by the other receiver 7". Thus, the lens 3' is moved up and forth and to the right and left in response to the focusing and tracking signals of the outputs of the respective amplifiers.