PURPOSE: To prevent vibrations except in focusing and tracking directions and to improve the positioning accuracy of a beam spot by slip-guiding a movable body built in a coil in a magnetic gap, and making said body movable only on some surface.

CONSTITUTION: A yoke 34 with a U-shaped section is erected on both sides of a base plate 32 where a through hole 30 for an optical beam lies in the center, and a permanent magnet 36 is stuck to the interior of the yoke to take for a magnetic circuit. Then the movable body 40 is inserted into the magnetic gap 38. A focusing coil 44 and a tracking coil 46 are contained in the frame body 42 of the movable body 40, and buried by a filler 48 so that the bottom of the coil 44 and the side part of the coil 46 can be positioned in the gap 38 and its center, respectively. Such a moving body 40 is suspendingly installed from both sides of a holding plate 52 mounting an objective lens 50. The movable body 40 is slidable in the focusing and tracking directions F and T. However, its movement in the gap length direction is regulated to prevent vibration.