An object of the present invention is to improve the quality level discrimination accuracy of the grain G by a grain quality level discrimination device. The device includes an optical unit 3 that emits light to the grain G, receives reflected and/or transmitted light from the grain G by a photosensor, and obtains information for discrimination of the quality level of the grain G from the upper and lower surface side of the grain G, and a quality level discrimination unit 7 that discriminates the quality level of the grain G on the basis of the information. The information on the upper and lower surface sides can be acquired by one optical unit at the same time so that the divergence therebetween due to the displacement or variation of the attitude of the grain G can be avoided. The reference plate for the correction of the information is placed outside of the moving path of the grain G to prevent it from soiling or damaging. Thus the deterioration of information can be avoided. Further, a reference plate esp
