PURPOSE: To provide a communication controller which is capable of utilizing the existing communication processing function on the side of a host device and supporting plural lines without being conscious of the incoming calls of the plural lines on the side of the host device.

CONSTITUTION: An incoming call number counter part 22 counts the number of the incoming call from plural communication lines, the arbitrary communication control process of a host device 1 accesses to a count value through a common control channel and a communication start command is issued as this access result through a logical channel. In a device control part 24, '1' is subtracted from the count value of the incoming call number counter part 22 and the line control part corresponding to a practically generated call is started, based on a communication start instruction command inputted via an I/F part 23. In this state, unless the count value is '0' also in the communication control process other than the communication control process issuing a command, the value is accessed and the communication start command can be issued.