A narrow-band observation image and a spectral estimation image are automatically switched based on the type of a subject. In an endoscopic image obtained by a scope, judgment is made as to whether the endoscopic image was obtained by close-up imaging or by distant-view imaging. When it is judged that the endoscopic image was obtained by distant-view imaging, white light is output from a light source unit and a spectral estimation image is output. When it is judged that the endoscopic image was obtained by close-up imaging, narrow-band light is output from the light source unit and a narrow-band observation image that has been obtained when the narrow-band light was output is output.
