PURPOSE: To eliminate the need for maintenance and control by a customer engineer by recording the update version of backup data in a version controller by a program for backup data generation and further writing version data on backup data filed in a backup file.

CONSTITUTION: A storage device 101 is stored with a program and/or data to be backed up. The program for backup data generation reads the program and/or data out of the storage device 10 to generate the backup data, which is recorded in the version controller 200 while written in the backup data storage area 312 and version storage area 311 of the backup file 310 together with the version through an external medium controller 300. A version comparing program 120 reads the version out of the version storage area 311 successively and compares it with the update version; when they are coincident, data are read out of the data storage area 312 to a backup data re-storing program 130 and backup data are rewritten in the storage device 101.