PURPOSE: To flatten the magnetic disk driving device by reducing the stacking size of the device and to provide the magnetic disk driving device capable of eliminating the chucking error of a floppy disk drive.

CONSTITUTION: This magnetic disk driving device has a rotor case 5 of a motor for rotationally driving a disk and a hub turn table 8 which is integrated with the rotor case 5, attracts the disk by a chucking magnet and rotates by holding the disk by such suction. The device is provided with the chucking magnet within the rotor case 5.