Endoscope apparatus

An endoscope apparatus comprising:

• an imager that detects reflected and scattered light of illumination light radiated to an observation object to output an imaging signal;
• and
• an illuminator that radiates illumination light including rays of narrow band light having different peak wavelengths or different central wavelengths,
• the rays of narrow band light included in the illumination light including
• emphasis narrow band light including a peak wavelength or a central wavelength in an emphasis wavelength range that includes, for an optical absorption spectrum of a diagnosis target substance present in the observation object, in any one color range of three color ranges, a first color range, a second color range, and a third color range, at least one of at least a maximum wavelength that takes at least a maximum value and a color-range largest wavelength that takes a color-range largest value that is a largest value of an optical absorption spectrum, and
• non-emphasis narrow band light having the peak wavelength or central wavelength that is included in a non-emphasis wavelength range that is a wavelength range that excludes the emphasis wavelength range from each of the three color ranges, and that has the peak wavelength or the central wavelength in a color range of the three color ranges that does not include the emphasis narrow band light.