To manage a storage medium, such as a USB memory which moves among a plurality of bases.

A user registers in advance to a management server, identification information physically added to the USB memory and a use location of the USB memory without using a data holding function of the USB memory itself to be carried out. Then, the management server generates a pair of asymmetrical encryption key/decryption key for encrypting/decrypting data in the USB memory, and issues only the encryption key to the user. The user performs encryption of the data on a user terminal using the issued encryption key, and performs when carrying out of the USB memory, automatic recording of entry/exit history of a use location to the management server. When using the USB memory, the management server checks an entry/exit history each time, issues the decryption key, and transmits the decryption key to the user. The user releases encryption using the decryption key.