An optical grain discriminating apparatus comprising: an inspection unit for performing an optical inspection on a grain to be transferred by transfer means; and a determination unit for discriminating between a good product and a defective product for the grain, based on the optical inspection by the inspection unit, wherein the inspection unit includes at least: a visible light source (15a, 15b) for irradiating the grain with visible light; a near-infrared light source (16a, 16b) for irradiating the grain with near-infrared light; a visible light detection unit (13a, 13b) for detecting visible light transmitted through the grain or visible light reflected from the grain; and a near-infrared light detection unit (14a, 14b) for detecting near-infrared light transmitted through the grain or near-infrared light reflected from the grain, and the determination unit plots wavelength components of red, green, and blue, and a near-infrared light component in a three-dimensional space, to create a three-dimensional optical correlation diagram, for a plurality of good product samples and a plurality of defective product samples, and thereby sets a threshold value, the wavelength components being detected by the visible light detection unit (13a, 13b), the near-infrared light component being detected by the near-infrared light detection unit (14a, 14b), wherein the determination unit plots two of wavelength components of red ®, green, and blue light, and the near-infrared light component in a three-dimensional space, to create a three-dimensional optical correlation diagram, for a plurality of good product samples and a plurality of defective product samples, and thereby sets a threshold value, the wavelength components being detected by the visible light detection unit (13a, 13b), the near-infrared light component being detected by the near-infrared light detection unit (14a, 14b), and wherein the determination unit plots a plurality of combinations of two wavelength components and the near-infrared light component in a three-dimensional space, to create a plurality of types of three-dimensional optical correlation diagrams, for a plurality of good product samples and a plurality of defective product samples, each of the combinations of two wavelength components including any two of wavelength components of the r ®, green, and blue light, the wavelength components being detected by the visible light detection unit (13a, 13b), the near-infrared light component being detected by the near-infrared light detection unit (14a, 14b). an inspection unit for performing an optical inspection on a grain to be transferred by transfer means; and a determination unit for discriminating between a good product and a defective product for the grain, based on the optical inspection by the inspection unit, wherein the inspection unit includes at least: a visible light source (15a, 15b) for irradiating the grain with visible light; a near-infrared light source (16a, 16b) for irradiating the grain with near-infrared light; a visible light detection unit (13a, 13b) for detecting visible light transmitted through the grain or visible light reflected from the grain; and a near-infrared light detection unit (14a, 14b) for detecting near-infrared light transmitted through the grain or near-infrared light reflected from the grain, and the determination unit plots wavelength components of red, green, and blue, and a near-infrared light component in a three-dimensional space, to create a three-dimensional optical correlation diagram, for a plurality of good product samples and a plurality of defective product samples, and thereby sets a threshold value, the wavelength components being detected by the visible light detection unit (13a, 13b), the near-infrared light component being detected by the near-infrared light detection unit (14a, 14b), wherein the determination unit plots two of wavelength components of red ®, green, and blue light, and the near-infrared light component in a three-dimensional space, to create a three-dimensional optical correlation diagram, for a plurality of good product samples and a plurality of defective product samples, and thereby sets a threshold value, the wavelength components being detected by the visible light detection unit (13a, 13b), the near-infrared light component being detected by the near-infrared light detection unit (14a, 14b), and wherein the determination unit plots a plurality of combinations of two wavelength components and the near-infrared light component in a three-dimensional space, to create a plurality of types of three-dimensional optical correlation diagrams, for a plurality of good product samples and a plurality of defective product samples, each of the combinations of two wavelength components including any two of wavelength components of the r ®, green, and blue light, the wavelength components being detected by the visible light detection unit (13a, 13b), the near-infrared light component being detected by the near-infrared light detection unit (14a, 14b).