A communication terminal device, interconnecting with a network system like the ISDN system, is configured by a CPU and a memory which stores calling identification numbers and called identification numbers with respect to communication companions who are registered in advance. Herein, one calling identification number and at least one called identification number are registered with respect to each communication companion. At a communication-sending event, a user designates a desired communication companion so that its calling identification number is automatically read out from the memory; and consequently, the communication terminal device automatically calls up the desired communication companion through the network system. At a communication-receiving event, the communication terminal device is informed of a calling party number corresponding to a calling party who accesses thereto through the network system. Then, the communication terminal device searches a called identification number, which coincides with the calling party number, within the called identification numbers registered in the memory. Thus, the calling party is identified based on the called identification number searched, so that the communication terminal device automatically performs a specific communication control which is set for the calling party identified.