PURPOSE: To prevent the file of another user from being erroneously processed by realizing control of a file user by a user control table.

CONSTITUTION: When a user password is inputted from an input means 1-3, a processing control means 1-4 reads the user password out of a user control table 1-9, which is read by a user control table processing means 1-8, and obtains usable file information. When a file processing command is inputted from the input means 1-3, the processing control means 1-4 analyzes the file processing command and executes deletion, registration and updating processing to the file, which is the object of processing, and the usable file information in the user control table 1-9 are updated through the user control table processing means 1-8. In such a way, the usable file information obtained by the processing control means 1-4 are outputted to an output means 1-10 and displayed. Thus, the file of the other user can be prevented from being erroneously selected.