To provide a disk driving device in which (A) the convenience of height adjustment is improved , (B) an optical pickup unit is easily attached, (C) the need of the height readjustment of a height adjusting screw is eliminated when the optical pickup unit is exchanged, and (D) a guide shaft is prevented from falling-off caused by external shocks or the like.

This device is provided with: a vertical positioning reference surface 32 for a positioning member 31 almost formed into a Z shape; and a guide shaft height adjusting mechanism 26 for a guide shaft 14 simultaneously pressed to the two places with the bottom end 34a of a height adjusting screw 34 attached to the upper end 31c of the positioning member 31 from two directions of arrows e and f by a pressing member 35 constituted of a spring member.