White light and excitation light are applied to an internal body part. An electronic endoscope captures a normal image of the internal body part irradiated with the white light, and a special image of autofluorescence emitted from living body tissue of the internal body part irradiated with the excitation light. An object distance detector detects an object distance between a CCD and an inspection area of the internal body part based on the normal image. A binning processing section applies a binning process to the special image. There are two types of binning processes, i.e. an intensity adjustment process and a resolution adjustment process. In the intensity adjustment process, the binning number is increased with increase in the object distance. In the resolution adjustment process, the binning number is decreased with increase in the object distance. Which process to perform is determined by operation on a processing type selector.