Crude protein contents of two types of polished rice, designedly polished in flat shape and polished in ordinary shape, were compared. The flat shape grains had lower crude protein contents than the ordinary shape grains, and this relation was more obvious at lower polishing ratio. The length, width and thickness of grains were measured on 42 samples of polished rice collected from 19 Sake factories. The length and width of grains gave good correlations with their polishing ratio, but the thickness did not. From the results mentioned above, it seemed that the thickness of rice grains is an important factor to evaluate the rice polishing process. Therefore, a new method of evaluation was devised, in which the width and thickness of grains can be measured by using originally designed sieves.