An endoscope includes an optical transmission module configured to convert each of the image pickup signal and the test signal into an optical signal and output the optical signal, and a signal amplitude measuring section configured to add signal amplitude information to the image pickup signal and the test signal, and a video processor includes an optical reception module configured to receive the optical signals and convert each of the optical signals into an electric signal and output the electric signal, an information acquiring section configured to acquire transmission information on each of the optical signals, the transmission information including the signal amplitude information, a determination section configured to determine a state of transmission of the optical signal, and a power supply adjusting section configured to adjust the applied voltage for the optical transmission module according to a result of the determination and output the applied voltage.