PURPOSE: To provide a flexible disk device improving assembling work.

CONSTITUTION: A metal bearing 18, a groove 39, a recessed insertion part 40 are provided on a guidance block 14 of a base part of a head supporting device 10. A leaf spring 35 is inserted into the recessed insertion part 40, and a small diameter pin 34 is inserted into the groove 39, and a screw part 47 of the base part 45 of a pressure member 36 is screwed to a screw hole 50 of a press plate 20, and the leaf spring 35 is left to be released without pressurizing. A lead screw shaft 30 of a head positioning device is inserted into the metal bearing 18 while setting the small diameter pin 34 free. After the mounting of the lead screw shaft 30 is ended, the pressure member 36 is rotated and advanced, and a part 43 to be pressurized of the leaf spring 35 is pressed to the bottom surface of the recessed insertion part 40, and the pressure part 42 of the leaf spring 35 is inclined upward. The small diameter pin 34 is raised by the pressure part 42 of the leaf spring 35, and is held in the state of being engaged with the lead groove 33 of the lead screw shaft 30.