To prevent illegal use embezzling a user ID and a password by registering a telephone number in a communication controller as well and collating all the telephone numbers in addition to the collation of the user ID and the password.

When a user 1 transmits a user ID (U-ID1) 6 and a password (P-W1) 7 according to the request of a communication controller 4 of a provider, they are stored in a temporary user ID storage register 9 inside the communication controller and a temporary user password storage register 10 inside the communication controller. According to the contents in the temporary user ID storage register 9 inside the communication controller, a user data register 13 is selected, and the respective correspondent user ID, passwords and telephone numbers of a temporary user data storage circuit 12 inside the communication controller and a user data register user 13 are compared and collated by a data collation circuit 26. When all the data are coincident, a GO signal is inputted to a network connection control circuit 27 and the connection of the user 1 to a network 5 managed by the provider is permitted.