PURPOSE: To minimize a whole thickness and to compact a device by supporting a floppy disk with a floppy disk holding surface itself formed at the inner ring itself of a roller bearing.

CONSTITUTION: When a floppy disk FD is inserted from an X direction while a rotary plate 10 and an inner ring 5 are rotated, a tip 11 is guided to a taper surface 8a and the tip 11 over the taper surface 8a arrives at a chamfering 5b and is guided smoothly. After insertion is completed, when a clamper 3 is moved downwards and a floppy disk FD is sandwiched with the clamper 3 and a floppy disk holding surface 5a, the floppy disk FD and the clamper 3 are also rotated. When a small diameter is executed for a roller bearing A in a limit, the bearing can also correspond to a recent considerable small diameter floppy disk FD and a whole thickness T1 can be remarkably thinner.