A video/sound signal switching and distributing device makes connections to a plurality of video/sound signal receiving devices to be connected at startup of a system and performs authentication between itself and the plurality of video/sound signal receiving devices, thereby acquiring key selection information about a video/sound signal transmitting device and holding the key selection information. Even when another video/sound signal receiving device is connected to the video/sound signal transmitting device while one video/sound signal is already in the middle of displaying a view of the video/sound signal, the video/sound signal transmitting device and the video/sound signal switching and distributing device can again establish a connection without redoing mutual authentication. Hence, disconnection and re-connection of the video/sound signal can be performed without interruption of the video/sound signal being displayed for viewing purpose.