To eliminate the influence of an offset in a middle point servo at the time of access by performing a middle point position servo based on the position signal of the radial direction of an optical disk of a light converging means and removing an offset component from this position signal.

A position signal generating circuit 31 calculates a position signal based on detection signals from respective light receiving surfaces of the light receiving part of a photodetector. Moreover, an offset removing means removes an offset portion from the position signal from the position signal generating circuit 31. A phase compensating circuit 33 compensates a diviation of phase imparted on the position signal at the time of removing the offset portion by a coupling capacitor 32. The position signal whose deviation of phase is removed is inputted to a DSP 34 as a changeover means and the DSP 34 selectively changes over the position signal from the circuit 33 and a tracking error signal. Then, it supplies the signal to the coil for tracking coil 35 of a biaxial actuator for the objective lens of an optical pickup.