A plurality of image transmitting apparatuses are connected to the image transmitting side of a transmission line, a plurality of image receiving apparatuses are connected to the image receiving side of the transmission line, and a plurality of logical channels are set on the transmission line. A predetermined logical channel is fixedly allotted to each image receiving apparatus, and each image transmitting apparatus is provided with a function of transmitting an image to an image receiving apparatus through any logical channel. Each image transmitting apparatus transmits an image to a designated image receiving apparatus through a predetermined logical channel.