A spectral image obtainment unit obtains spectral image data by receiving reflection light in different wavelength bands, into which light reflected by a living body mucous membrane has been separated, at a light receiving unit by causing a ratio of a light receiving level in a short wavelength band with respect to a light receiving level in a long wavelength band to be greater than a ratio of spectral reflectance in the short wavelength band at the living body mucous membrane with respect to spectral reflectance in the long wavelength band thereat. A spectral image data operation unit performs a spectral image estimation operation by correcting the value of the spectral image data to that of spectral image data obtained by receiving light without causing the ratio to increase. Accordingly, a diagnostic spectral image of the living body mucous membrane is obtained in an electronic endoscopic apparatus.