An electronic endoscope transmits an image pickup signal converted into digital serial data, as a differential signal, to a processor such that a quality of an output waveform to the processor is fixed, and includes: a first transmission section； a first filter section arranged at an output side of the first transmission section, wherein a constant is adjusted according to a loss in a transmission channel including a cable disposed in a part from the first transmission section to the first filter section； a second transmission section for transmitting the differential signal from the first filter section to the processor； and a second filter section arranged at an output side of the second transmission section, wherein a constant is adjusted according to a loss including a cable located in the second transmission section or in a portion subsequent to the second transmission section.
