File migration device

In a network system in which clients and file servers are connected by networks and a client makes access to a file stored in a disk storage device of a file server via the networks, accessibility to a file of a file server distant from the client tends to be deteriorated. In order to resolve the problem, the file server having the file searches for an appropriate file server in the proximity of the client and transfers the file to the appropriate file server (migration target server). Thereafter, the client makes access to the migration target server for the file.