A facsimile communication system and a communication apparatus reduce a loss time due to the synchronization of transmission/reception and shorten a communication time. They also shorten a communication time in a full duplex communication mode and allow proper switching of the full duplex communication at the transmission/reception replacement. DIS-CFR signals, EOP-DCN signals, NSS-TSI signals and TSI-DCS signals of a facsimile communication protocol are connected by synchronization signals so that the synchronization signals are sent even after the sending of the protocol signal. Thus, the sending of the synchronization signal for one second when the next protocol signal is sent is not necessary and a time required for the protocol signal is shortened. An ANSam signal to disable a function of an echo suppressor is sent when a call is detected and a calling station thereafter sends a protocol signal and an image signal in a manner not to cause signal interruption of 50 ms or longer, and at transmission/reception replacement at the end of the image signal from the calling station, a called station sends an ANSam signal and sends a protocol signal.