PURPOSE: To prevent the user's information written on a magnetic tape from being transferred by managing the magnetic tape medium housed in the magnetic tape library device by the device alone and rewinding the magnetic tape medium in the magnetic tape library device itself.

CONSTITUTION: A magnetic tape medium management storage area 2 is provided in the magnetic tape library device 1, and when the magnetic tape medium is supplied on this area in the device, information of the magnetic tape medium is stored. Then, rewinding can be processed on the magnetic tape medium by the magnetic tape library device 1 itself by referring to the stored information in a specified period.