A video transmission system, in which a transmission device, a video signal source, and a video reception device are connected with each other via HDMI (High-Definition Multimedia Interface) which transmits uncompressed video signal; the transmission device verifying whether or not the video signal source and the video reception device have a function of transmitting/receiving a message and enabling the function of transmitting/receiving the message between the video signal source and the video reception device when both the video signal source and the video reception device have the function of transmitting/receiving the message; and the function of transmitting/receiving the message between the video signal source and the video reception device being terminated when HPD (Hot Plug Detect) signal indicated by the video reception device is set to “L” level.