An electronic endoscope system comprises a video-scope, an imaging device, and a black balance processor. The imaging device, which is provided on the video-scope, is exposed at a normal shutter speed so as to generate an image signal corresponding to an optical image that is formed thereon. The black balance processor generates a black balance value for adjusting the black balance of the image signal, based on a black image signal corresponding to a black image. The black image signal is generated by exposing the imaging device at a high shutter speed that is faster than the normal shutter speed.