PURPOSE: To boil polished rice by a rice cooker only by addition of water by a user by specifying temperature of warm water, immersion time and drying state of polished rice of material, drying, sealing and packaging polished rice of material.

CONSTITUTION: Polished rice of material is washed with warm water at 60-80°C not to make grain temperature exceed 50°C for 3-6 minutes including immersion time, rapidly dried while grain temperature is being kept at ≥30°C, sealed and packaged. In order to prevent grain cracking of polished rice after washing and immersion in water of rice, the polished rice is dried by a proper dryer before the grain temperature is dropped to ≤30°C and the dried rice has to be sealed and packaged. The drying process is to prevent the treated polished rice from containing more than a necessary amount of water and from becoming a swollen state. The treated polished rice can be wholly softly and tastily boiled without casing grain cracking and half-boiled rice. Further the polished rice has excellent shelf stability up to boiling by users.