PURPOSE: To delete unnecessary subfiles which are present on a library device.

CONSTITUTION: A library control input device 400 supplies information on dates and library names which can not be deleted to a library control information storage means 20. A library control information device 300 has the information on the dates and subfile names which can not be deleted. A library control information storage means 20 stores the library control information device 300 with information from a library control information input device 400. A library control means 10 retrieves the information of the library control information device 300 from deletion indication information of an indication input device 100 and matches it to delete only subfiles which can be deleted from a library device 200. Consequently, a wrong deletion indication from an indication input device 100 is eliminated to improve the security of the library device 200.