PURPOSE: To prevent an optical axis from being fallen, etc., by forming plural air chambers to a lens farm by a piston and a cylinder and forming an air bearing by the lens frame and the air bearing.

CONSTITUTION: When a coil 6 is energized, a suction or repulsion magnetic field is generated between yokes 26 and 27 and the coil 6 is shift risingly or dropping in an A direction. Since a lens frame 2 is also united to a coil bobbin 7, the lens frame 2 is also shifted risingly or droppingly under the support of plate springs 10 and 11 and the position of an objective lens 1 is adjusted. At the time of this action, at the time of the shifting action, air in the air chamber 19 gets into and out of an air gap 21 formed by a piston 17 and a cylinder 20 and it operates as air damper. An air bearing 24 is formed between the lens frame 2 and the air bearing 23, the lens frame 2 is slidingly shifted while being constrained in its radius direction by compressed air supplied from an air supplying hole 25 and good straightness of light along an optical axis can be obtained.