PURPOSE: To permit efficient drying while reducing the deterioration of quality of rice as much as possible by a method wherein far infrared rays, having a specified wave length, are utilized and the surface temperature of unhulled rice is maintained at a temperature lower than a predetermined value.

CONSTITUTION: As the result of experiment, the absorbing degree of unhulled rice with respect to far infrared rays becomes higher than the absorbing degree of chaff with respect to the same when the wave length of far infrared rays is 5.7-9.1μm. Accordingly, far infrared rays, having the range of wave length of 5.7-9.1μm, are projected against the unhulled rice whereby efficient drying is permitted by making the temperature of the external chaff higher than the internal unhulled rice while restraining the temperature rise of the internal unhulled rice and preventing the deterioration of the quality of rice due to heating. On the other hand, the temperature of chaff is maintained lower than 50°C, which is lower than the same temperature used so far, so as to maintain the temperature of the unhulled rice at a temperature lower than 40°C, whereat the deterioration of the quality of the hulled rice can be restrained, by utilizing a fact that the temperature of the unhulled rice is proportional to the temperature of the chaff with a constant rate.