PURPOSE: To prevent the disk jacket of a floppy disk from oscillating by positioning the disk jacket at a specified loading position with a positioning means and providing a clamping means which clamps the jacket with elastic force.

CONSTITUTION: The floppy disk 2 is inserted as shown by an arrow (x). A guide shaft 11 is fitted to the rotating end part of a clutch plate 6, and this is fitted at both ends in a longitudinally long guide groove provided to the housing of a magnetic recording device to specify the motion of the clutch plate 6. Then, this guide shaft 11 is fitted to an x-directional presser spring 12 which presses the floppy disk 2 in its insertion direction (x) from an insertion/extraction opening side.