An electronic endoscope apparatus includes: an electronic endoscope having a power amplifier for transmitting by radio or by cable an image pickup signal obtained from an image sensor; and a low noise amplifier for receiving the image pickup signal transmitted by radio and by cable. The apparatus further includes: a processor unit for producing a video signal from the image pickup signal; and a cable connection detection circuit for changing gain of the power amplifier or gain of the low noise amplifier, upon detecting a connection of a cable between the electronic endoscope and the processor unit, for transmitting the image pickup signal by cable.