An optical grain evaluation device comprising: a light source; a light-projecting means configured such that light from the light source is projected therethrough to stored grain; a light-receiving part configured such that light that has been projected to the grain through the light-projecting means and transmitted through the grain is incident thereon, the light-receiving part being lined up on the same plane as the light-projecting part at a distance therefrom; a grain evaluation unit configured to evaluate the grain based on the light received by the light-receiving part; and a shielding part that separates a region between the light source and the light-projecting part from a region between the light-receiving part and the grain evaluation unit, so as to prevent light from the light-projecting means from directly entering the light-receiving part, wherein the region between the light source and the light-projecting means, and the region between the light-receiving part and the grain evaluation unit are configured, over the entirety of the regions, as air transmission regions in which light is transmitted through air; wherein the optical grain evaluation device further comprises: a shutter that is switchable between an open state in which the light from the light source is allowed to pass through the light-projecting means, and a closed state in which the light is prevented from passing through the light-projecting means; and a correction mechanism configured, when the shutter is in the closed state, to take in the light from the light source and obtain light information for use in correcting an evaluation result regarding the grain, wherein the shutter and the correction mechanism are provided to be movable together; and wherein the correction mechanism is provided with a correction optical filter (140, 141) configured such that the light from the light source taken in by the correction mechanism passes through the filter to generate the light which passes to enter the grain evaluation unit. a light source; a light-projecting means configured such that light from the light source is projected therethrough to stored grain; a light-receiving part configured such that light that has been projected to the grain through the light-projecting means and transmitted through the grain is incident thereon, the light-receiving part being lined up on the same plane as the light-projecting part at a distance therefrom; a grain evaluation unit configured to evaluate the grain based on the light received by the light-receiving part; and a shielding part that separates a region between the light source and the light-projecting part from a region between the light-receiving part and the grain evaluation unit, so as to prevent light from the light-projecting means from directly entering the light-receiving part, wherein the region between the light source and the light-projecting means, and the region between the light-receiving part and the grain evaluation unit are configured, over the entirety of the regions, as air transmission regions in which light is transmitted through air; wherein the optical grain evaluation device further comprises: a shutter that is switchable between an open state in which the light from the light source is allowed to pass through the light-projecting means, and a closed state in which the light is prevented from passing through the light-projecting means; and a correction mechanism configured, when the shutter is in the closed state, to take in the light from the light source and obtain light information for use in correcting an evaluation result regarding the grain, a shutter that is switchable between an open state in which the light from the light source is allowed to pass through the light-projecting means, and a closed state in which the light is prevented from passing through the light-projecting means; and a correction mechanism configured, when the shutter is in the closed state, to take in the light from the light source and obtain light information for use in correcting an evaluation result regarding the grain, wherein the shutter and the correction mechanism are provided to be movable together; and wherein the correction mechanism is provided with a correction optical filter (140, 141) configured such that the light from the light source taken in by the correction mechanism passes through the filter to generate the light which passes to enter the grain evaluation unit.