PURPOSE: To realize high-precision photometry by providing a light shield body at a position conjugate to the edge of a distribution part about a condenser lens, and removing its scattered light and preventing the mixture of unnecessary information.

CONSTITUTION: Light shield bodies 7aW7d are installed at positions conjugate to edges 2aW2d of the distribution part 2 with respect to the condenser lens 4. Then, irradiation light converged on an object body S through the lens 2 is scattered by the object body S and then converged on a photoelectric detector 6 through a condenser lens 4, but scattered light from the edges 2aW2d is cut off by the light shield bodies 7aW7d, and further scattered light from the periphery of the distribution part 2 is removed by an aperture 5, so that the photoelectric detector 6 photodetects only scattered light from the object body S. Consequently, high-precision photometry is performed.