To smoothly send image data with high definition and to reduce the transmission time of the image data by sending in parallel the image data to image transmitters with a multi-point control unit.

Image data by the HDTV system are outputted onto a network line from an image transmitter 110. The image data are sent from the transmitter 110 to a multi-point control unit MCU 301. The MCU 301 stores the image data to a storage device, then the CPU of the MCU 301 reads out the stored image data and sends the data to an image transmitter 120 and then sends the same image data to an image transmitter 130 and the repeats the operation above to image transmitters 140-190 sequentially. Thus, the image data sent from the transmitter 110 are sent to the other transmitters 120-190.