To secure secrecy by optionally restricting the range of common files by defining paths allowed as common files for a system having a tree structure so that they correspond to search identifiers and allowing a system which does not have a tree structure to access by specifying a search identifier and the common file name under its control.

A definition body 2 is set by previously defining paths up to directories which are allowed to be accessed corresponding to search identifiers 3. At a request for a list wherein a file name is specified from a client 11 as an access source, a server 1 generates and sends a list of the names of all path files having a specified file name to the access source and the client 11 displays the list of the path file names on a display device 17. Then, a selected file name is sent to the server 1, which accesses the file having the file name in a uniquely specified tree structure from a common file device 6.