An illumination apparatus includes: a light source that emits light at a plurality of wavelengths; and a rod-like light guide that shapes light emitted by the light source into a line, wherein the light guide is made of a material including a region in which transmittance of wavelengths is not constant, the light source is arranged at one end of the light guide in a longitudinal direction, the light source includes a wavelength of a region in which transmittance of the light guide is not constant, and a reflection surface including reflection member having reflectance differences for the light at a plurality of wavelengths is formed at the other end of the light guide in the longitudinal direction.