the negotiation with the destination terminal of transfer or when the default local port number that is to be used by the destination terminal of transfer is occupied at present the record erasing section 102 15 detects the extension number or the local ip address of the terminal that has terminated a communication if the record erasing section 102 15 detects the extension number of the terminal that has terminated a communication the record erasing section 102 15 retrieves the local ip address that corresponds to the extension number from the extension number versus local ip address correspondence table 102 2 the record erasing section 102 15 also detects the type of the communication that has been terminated or the local port number used for the communication that has been terminated if the record erasing section 102 15 detects the type of the communication that has been terminated the record erasing section 102 15 retrieves the local port number that corresponds to the type of the communication from the local port number storage section 102 4 if for example the type of communication is limited to ip telephony and the local port number is fixed the record erasing section 102 15.