To provide a disk device having a function of effectively avoiding an influence of an external magnetic field without spoiling lightweight and thin constitution of a primary disk drive body by reducing disabled design alterations etc., while making assembling facilities common and suppressing a rise in manufacturing cost.

The magnetic disk drive is characterized in having a motor which has a case and a rotatable hub and is provided in the case, a disk which has an internal hole into which the hub is inserted and is fitted around the outer periphery of the hub, a head performing information processing for the disk, and an annular shield member which comes into contact with the hub and extends outward radially from the hub to be opposed to the surface of the disk at a prescribed distance, and is made of a high magnetic material in nearly the same shape with the disk.