To provide an apparatus capable of measuring polarized light in a short time and with good accuracy and with high sensitivity.

This measuring apparatus 100 is provided with a reaction part installing part 142 for holding a reaction part 120 and a reaction part temperature control part 144 for controlling the temperature of the reaction part 120. The reaction part 120 is a closed cell, which has a space for storing a tested material and a reactive solution containing a reagent or the like and a penetrating hole for putting the reactive solution in the space. The measuring apparatus 100 is further provided with a light source part 102 for emitting a light beam toward the reaction part 120, a polarizer 104, an analyzer 106, and a photo detector 108 for detecting light transmitted through the analyzer 196. The light source part 102 and the polarizer 104 are disposed so that the optical axis makes a designated angle to the surface of the reaction part 120. Similarly, the analyzer 106 and the photo detector 108 are disposed so that the axis makes the same angle to the surface of the reaction part 120.