An endoscopic illumination system includes at least two light sources, an illumination system, a multiplexer, at least two detectors, and a light source controller. The multiplexer includes at least two input ports and an emission port. The multiplexer can propagate light that is input from the input ports to the emission port separately or after multiplexing the light. The multiplexer can output a portion of light propagating between the input ports and the emission port. The detectors detect the light propagating between the input ports and the emission port in each wavelength band. The light source controller adjusts the amount of light emitted from the light sources. The amount of light emitted from each light source is thereby appropriately adjusted even when multiple light sources are turned on simultaneously.
