The invention enables a magnetic disk drive to be inserted and removed against an attraction force exerted by a magnetic force that is strong enough to erase data on a magnetic disk enclosed within a metal case. A converting mechanism comprising a ballscrew and a ballscrew nut bracket is provided that converts rotational motion of a handle into translational motion of an HDD holder; by rotating the handle, the HDD holder with the hard disk drive mounted thereon is moved in the inserting and removing directions by overcoming the attraction force being exerted by the magnetic field generated by means of a permanent magnet. An electric motor may be used to generate the rotational force.