An accurate spectral estimation image is generated at high speed. When a wavelength set (CH1 through CH3) is set through an input means (2), ON/OFF of light emitting devices (10a through 10d) is controlled based on the set wavelength set (CH1 through CH3). Further, a subject (S) illuminated with light of a predetermined wavelength band or bands are imaged by a scope (20) to obtain an endoscopic image (P) . Matrix operation is performed on the endoscopic image (P) to generate a spectral estimation image (SP).
