PURPOSE: To obtain a focus servo introducing circuit and a method which are stable and high in response speed.

CONSTITUTION: An objective lens is moved within distance of a prescribed range from a recording medium by an output signal S1 of a 1st low frequency oscillator circuit 111, and is subsequently oscillated by an output signal S2 of a 2nd low frequency oscillator circuit 113, and at the moment that the objective lens passes a focusing point, a focus servo means is operated. Since the passing speed of the objective lens through the focusing point can be reduced by these two steps of oscillation, the stable focus servo can be set up.