A sorting apparatus is disclosed which utilizes transmitted light to determine whether or not an article under inspection is defective in order to reject any article determined to be defective. A light irradiator is provided on irradiating an article being inspected with a light beam having a smaller diameter than that of an article, and a light condenser is provided for condensing the rays of light transmitted through the article while being diffused. Two light detectors respectively detect two specific kinds of light having different wavelengths from among the condensed rays of light transmitted through the article. A ratio is obtained between the intensities of the two specific kinds of light detected by the light detector and compared with a predtermined ratio in order to determine whether the article under inspection has undergone deterioration in quality.
