An HDMI optical conversion device comprising: a transmission device side connector to be connected to an HDMI transmission device; a reception device side connector to be connected to an HDMI reception device; and a cable connecting the transmission device side connector and the reception device side connector, the cable including an optical fiber wire configured to transmit a video signal, wherein the reception device side connector includes: an optical receiver configured to convert an optical signal transmitted by the optical fiber wire into an electric signal; a reception device side video transmission line configured to transmit the electric signal as a video signal output from the optical receiver to the HDMI reception device; and a detection sensor configured to detect a voltage of the reception device side video transmission line and output a detection signal, wherein the cable further includes: a dedicated electric wire configured to transmit the detection signal output from the detection sensor, and wherein the transmission device side connector includes: an optical transmitter configured to generate an optical signal to be transmitted by the optical fiber wire; a transmission device side video transmission line configured to transmit an electric signal as a video signal output from the HDMI transmission device to the optical transmitter; and a voltage converter configured to receive the detection signal transmitted by the electric wire and change a voltage of the transmission device side video transmission line based on the received detection signal. a transmission device side connector to be connected to an HDMI transmission device; a reception device side connector to be connected to an HDMI reception device; and a cable connecting the transmission device side connector and the reception device side connector, the cable including an optical fiber wire configured to transmit a video signal, wherein the reception device side connector includes: an optical receiver configured to convert an optical signal transmitted by the optical fiber wire into an electric signal; a reception device side video transmission line configured to transmit the electric signal as a video signal output from the optical receiver to the HDMI reception device; and a detection sensor configured to detect a voltage of the reception device side video transmission line and output a detection signal, an optical receiver configured to convert an optical signal transmitted by the optical fiber wire into an electric signal; a reception device side video transmission line configured to transmit the electric signal as a video signal output from the optical receiver to the HDMI reception device; and a detection sensor configured to detect a voltage of the reception device side video transmission line and output a detection signal, wherein the cable further includes: a dedicated electric wire configured to transmit the detection signal output from the detection sensor, and a dedicated electric wire configured to transmit the detection signal output from the detection sensor, and wherein the transmission device side connector includes: an optical transmitter configured to generate an optical signal to be transmitted by the optical fiber wire; a transmission device side video transmission line configured to transmit an electric signal as a video signal output from the HDMI transmission device to the optical transmitter; and a voltage converter configured to receive the detection signal transmitted by the electric wire and change a voltage of the transmission device side video transmission line based on the received detection signal. an optical transmitter configured to generate an optical signal to be transmitted by the optical fiber wire; a transmission device side video transmission line configured to transmit an electric signal as a video signal output from the HDMI transmission device to the optical transmitter; and a voltage converter configured to receive the detection signal transmitted by the electric wire and change a voltage of the transmission device side video transmission line based on the received detection signal.