A light source portion 41, which is connected to a control portion 42 and an endoscope 101, radiates a pre-determined light quantity of white light based on a signal from the control portion 42. The light source portion 41 includes a lamp 15 as a white light source, an infrared cut filter 15a, a light quantity limiting filter 16, being inserted/removed on an optical path, for limiting light quantity in a pre¬determined wavelength region of white light, a filter insertion/removal driving portion 17 for inserting/removing the light quantity limiting filter 16 on an optical path, and a condensing lens 18 for outputting white light. For example, when a transmission rate of a blue band is 100 %, the light quantity limiting filter 16 limits transmission rates of other bands to 50 %. This improves S/N in discrete spectral image generation with illumination light in a visible light region.
