Disclosed is an Internet FAX apparatus which, after receiving an Internet address from a certain destination, can communicate with the same destination in later transmission or during communication by connecting to a LAN and switching to an Internet FAX mode requiring no communication charge. An Internet facsimile apparatus on the receiving side transmits its Internet facsimile function and Internet address on an NSF signal in a standard protocol of G3 facsimile transmission and/or transmits its telephone number, Internet facsimile function, and Internet address on TSI and NSS signals in the standard protocol of G3 facsimile communication. The Internet facsimile apparatus registers an Internet facsimile function and Internet address of a partner apparatus as destination data. The Internet facsimile apparatus communicates with the partner apparatus by using the Internet address in the destination data in later transmission or by disconnecting ordinary facsimile mode communication and switching to the Internet FAX mode.