PURPOSE: To shorten the development period of the communication controller attended with a content of a new communication line by using an existing communication protocol processing section for transfer of operating control information and line control without modification.

CONSTITUTION: The communication controller 11 is provided with a line adaptor 61 accommodating a new communication line 21C and relevant protocol processing sections 53, 53A. The communication protocol processing section 53 copes with a command to the line adaptor 61 corresponding to the new communication line 21C and also a command to an old type line adaptor corresponding to an existing communication line. In this case, a same item is commanded in duplicate, and a line control operating means 612 adopts information of 'communication line speed' stored in an operation control information storage means 611 with priority and is operated based thereon and disregards information of 'communication line speed' from the communication protocol processing section 53 via a line control bus 712.