Digital image transmission system using single line and image transmission method therefor

According to the present invention, disclosed is a digital image transmission system using a vertical regression section of a vertical signal to transmit and receive a signal by using a single line. The system comprises: a first device, using a first signal, to transmit a video signal when the first switch is operated in a first mode, and to transmit a remote signal from the outside when the first switch is operated in a second mode; and a second device, using a second switch, to receive the video signal from the first device when the second switch is operated in the first mode, and to transmit the remote signal to the first device when the second switch is operated in the second mode. Switching of the first and the second switch from the first mode to the second mode uses a starting time point of a vertical regression section of the video signal.