To stabilize a servo gain even when it is thinned by adjusting wire winding states of respective coils or a magnetization state of a magnet so that electromagnetic force obtained by making flow a current through a focus coil or a track coil of an objective lens drive mechanism is uniformized regardless of a position of a magnetic field.

The focus coil 3 and the track coil 4 drive an objective lens in the focus direction and the track direction by currents flowing through each and magnetic flux of a pair of magnet 8 stuck to a yoke 9. Since the magnetized property of the rectangular magnet 8 is different according to the position, magnetic flux density is reduced in a central part, and the generated electromagnetic force is changed greatly according to coil movement. Then, the amount of electromagnetic force reduced in the central part of the magnet 8 is compensated by increasing the number of winding wires of the central part of the focus coil 3, and increasing the current traversing the magnetic flux, and the electromagnetic force is uniformized. Thus, the servo gain is stabilized in the movable areas of respective coils.