An illumination apparatus includes a light source including a semiconductor laser that emits coherent light, a polarization splitter including rutile, a half-phase retardation film, and another rutile to split optical paths by the polarization direction of incident light, and a projection polarization switching mechanism including a half-wave plate unit, a quarter-wave plate unit, and a polarizing film to switch projected light emitted from the polarization splitter between polarization components of light transmitted over optical paths split by the polarization splitter and a polarization component of light transmitted over any one optical path. As a result, a compact illumination apparatus, and a measurement apparatus using the same, with a common light source and optical system for both observation light and measurement light can be provided.
