PURPOSE: To obtain a video output transmitting device of simple constitution by providing a booster that amplifies idle channel video output of a TV receiving set sent out from a VTR etc., a linear amplifier that obtains specified power output and a transmitting antenna.

CONSTITUTION: A video output terminal 2 of a VTR1 is connected to the booster 3, and video output of idle channel of a TV receiving set is sent out from the terminal 2. The video output is amplified by the booster 3 as it is and inputted to the linear amplifier 4 through an attenuator 5. Output amplified by an amplifier 4 to obtain specified electric power is supplied to an antenna 7 through an LPF6, and radio waves of idle channel are sent out from the antenna 7. Video of the VTR1 can be reproduced by setting the TV receiving set 10 installed at a proper position off from the VTR1. An RF modulator 11, a microcomputer game machine 12, a personal computer 13 etc. can be connected to the input of the booster 3.