The present invention eliminates variations in the engagement between a rack and a pinion, which drive a recording head, to enable the head to move speedily and smoothly. A head driver includes a rack provided on a recording head that slidingly moves over a recording disc and a pinion engaged with the rack and rotated by a drive motor, wherein there are provided a concave groove, provided on the rack and running in parallel with rack tooth, and a swing arm with which a rigid guide, guided by the concave groove, is integrated and on which a rotation axis of the pinion is provided. When the rack is at a slant with the movement direction, the swing arm swings, following the slant of the rack to keep constant the spacing between the rack and the pinion.