An endoscope apparatus comprises: an endoscope comprising an imaging device that forms color image signals of a body to be observed; a Y/C signal processing circuit that forms brightness/color difference signals from a color image signal obtained by the imaging device; a storage portion that stores Y/C matrix data for forming a spectral image based on the brightness/color difference signals; and a Y/C spectral image forming circuit that conducts matrix calculation by the Y/C matrix data of the storage portion and the brightness/color difference signals output from the Y/C signal processing circuit and forms a spectral image of an arbitrarily selected wavelength range.