PURPOSE: To completely cut off dust entering the inside of an optical head and to improve the reliability of an optical system on the lens positioner mechanism, so called, the focus actuator of various kinds of an optical disk devices and a magneto-optical disk devices.

CONSTITUTION: A lens holder 15-1 is inserted into a through hole 16-1a so that a coil 15-2 provided on the outer peripheral surface of the lens holder 15-1 attaching an objective 4-3 to one end side in parallel with each other and a permanent magnet 16-2 arranged in the recessed part of a focus base 16-1 consisting of magnetic material are faced each other at a fixed interval. This device is constituted so that both end edges of the lens holder 15-1 and both surfaces of the outer peripheral part of the focus base 16-1 are coupled with two sheets of leaf springs 17 and the objective 4-3 of the lens holder 15-1 follows up an optical disk rotating at a fixed interval by applying current through the coil 15-2.