1. An electronic endoscope system, comprising: a light source device for applying illumination light to an internal body part, said illumination light including special light in a specific wavelength band; an electronic endoscope for capturing an endoscopic image of said internal body part irradiated with said illumination light by using an image sensor, said endoscopic image including a special image captured under said special light; an object distance detector for detecting from said endoscopic image an object distance including a distance between said image sensor and an inspection area of said internal body part; a binning processing section for applying a binning process to said special image; and a binning processing control section for determining a binning number used in said binning process in accordance with said object distance, wherein said illumination light includes normal light including white light ranging from a blue wavelength band to a red wavelength band, wherein said endoscopic image includes a normal image of said internal body part irradiated with said normal light, and wherein said object distance detector obtains said object distance from said normal image.