The object of the invention is to provide an infrared circular dichroism measuring apparatus that improves the measuring time and the measuring accuracy.
An infrared circular dichroism measuring apparatus 101 comprising: AC signal extractors 110-112 where an interference light beam from an IR light source 102 which has passed an interferometer 103 is converted into a clockwise and a counterclockwise circularly polarized light beams and is irradiated on a sample to extract from a detected signal of detector 107 an interferogram by each of the circularly polarized light beams; DC signal extractors 113, 112 for extracting an interferogram by the IR absorption of the sample; a calculator 114 for figuring out the circular dichroism; and a selective transmitter 120 for narrowing down the wavelength region to be measured based on an IR absorption wavelength region corresponding to a vibration mode of the structure to be measured in the sample molecule.