An endoscope processor including a light source controller, an imaging device driver, and a gamma-correction block, is provided. The light source controller can order first and second light sources to alternately emit first and second lights, respectively. The imaging device driver orders an imaging device to generate first and second image signals by capturing an optical image of a subject while the firs and the second light are shone on the subject, respectively. The gamma-correction block carries out gamma correction on the first and second image signals using first and second color gamma coefficients, respectively. The first and second color gamma coefficients are predetermined according to the wavelength band of the first and second lights.