An electronic endoscope removably connected to a video processor in which a predetermined gamma characteristic is set includes: an image pickup device provided at a distal end of an insertion portion configured to be inserted into a subject, the image pickup device being configured to pick up an optical image of the subject to generate an image pickup signal; a gain circuit configured to amplify the image pickup signal using a predetermined gain parameter; a gamma characteristic recognition circuit configured to recognize the gamma characteristic of the video processor; and a gain adjustment circuit configured to set the gain parameter according to the gamma characteristic.