To change a multicast address as required.

A camera video image monitor system is provided with image distribution devices 2-1 and 2-2 for distributing video images obtained by monitor cameras 4-1 and 4-2 through a network 1 and video image display terminals 3-1 and 3-2 for taking in and displaying images distributed from the image distribution devices 2-1 and 2-2 through the network 1 and distributes the video images by multicast addresses, and a change means 6 is provided which changes multicast addresses used for sending video images from the video image distribution devices 2-1 and 2-2.