In the Internet facsimile communication system, to exchange the functions of one another between the transmitting side and the receiving side, the Internet facsimile machine 20 carries out facsimile communication by using an electronic mail via the Internet. The principal control unit 1 exchanges the ability of the facsimile machine with that of the other end by using the electronic mail with the same communicating procedure as the communicating procedure of ITU-T recommendation T-30 used in the facsimile communication, and transmits an image data according to the exchanged ability of each facsimile machine. The electronic mail includes the FAXID (facsimile communication identifying number) which is the data for identifying the series of facsimile communication.