PURPOSE: To reduce an energy consumption at the time of a high-speed travelling by arranging a tracking driving coil in a tracking driving magnetic circuit having a magnetic gap in the turning direction of a turning member and composing the turning member of a non-conductive material.

CONSTITUTION: An objective 100 is fixed to an objective holding member 102 so that the optical axis can be made parallel to a focusing direction 1001. To a tracking driving magnetic circuit 144, a tracking driving magnet is fixed, and a magnetic flux is generated in a direction parallel to the focusing direction 1001 to the magnetic gap of the magnetic circuit 144. By impressing a tracking driving signal to a tracking driving coil 116 fixed to a turning member 152, the turning member 152 is driven in a tracking direction 1002. The turning member 152 is composed of the non-conductive material, and even at the time of moving the objective 100 at a high speed, a loss due to an eddy current, etc., cannot be generated, and the energy consumption at the time of the high- speed traveling can be reduced.