In an endoscope apparatus in which a scope is connected to a processor unit in a freely attachable and detachable way, the endoscope apparatus wherein matrix calculation is conducted for RGB signals formed by using CCD, a color space conversion processing circuit is provided for forming spectral images of the arbitrarily selected wavelength range. CCD characteristics identification information including types of color filters of the CCD and spectral characteristics or scope characteristics information is stored in the ROM of the scope, a plurality of matrix data corresponding to characteristics identification information is stored in the memory of the processor unit, and matrix data corresponding to the obtained characteristics information is read from the memory, thereby forming an excellent spectral image by using data suitable for characteristics of the CCD or the scope.