An electronic endoscope 2 transmits an image pickup signal obtained by an image pickup section 14 and converted into digital serial data, as a differential signal, to a processor 3, and includes a transmission section 15 for transmitting the differential signal to the processor 3, and a filter section 16 arranged at an output stage of the transmission section 15, wherein a constant of the filter section is adjusted according to a loss in a transmission channel including a cable such that a quality of output waveform to the processor 3 is fixed.
