PURPOSE: To obtain a determining method of the quality of unhulled rice wherein the quality of the unhulled rice is determined on the basis of the value of the quantity of light detected from a light beam applied to each grain of the rice and wherein the brand of the rice is determined on the basis of a quality evaluation value obtained as the result of the fore-going determination.

CONSTITUTION: Unhulled rice of a high water content is dried by heating for a short time by a microwave or hot air. The unhulled rice of high water content thus treated is hulled to be unpolished rice 1 by an impeller-type huller. A light is applied to each one grain of the unpolished rice thus obtained and the quality of the unpolished rice 1 being a sample is determined on the basis of detected values of the quantity of transmitted light, the quantity of reflected light, etc. The light is applied to each grain of the rice, the quantity of transmitted light, the quantity of reflected light, etc., are detected and the constituent is determined from the detected value of each quantity of light. The constituent thus determined is subjected to a statistical processing, compared with a quality evaluation value and thereby the kind or mixing-in of another kind is determined.