PURPOSE: To prevent malfunction at the lead-in time of automatic focusing control by providing the titled device with stoppers for restricting the movement of an objective lens.

CONSTITUTION: A stopper 61 for determining the lower limit position of an objective lens and a stopper 62 for determining the upper limit position are formed to locate the focal position of the objective lens at the shunting time in an optical disc base material 11. At the lead-in time to automatic focusing, the moving range of the objective lens is reduced less than twice the thickness of the optical disc base material 11 so that the focal position of the objective lens does not cross the surface of the optical disc base material 11. Since the opposite side of the recording side 12 of the optical disc base material 11 is not detected, a differential amplifier can output only the S-shaped characteristics obtained from the real recording side 12. Therefore, the focal position of the objective lens can be prevented from being set in a side other than the recording side.