Degree of gelatinization during cooking of Akibare(Janponica) and Milyang 23 (Indica) rice was determined by X-ray diffractometry using a buit-in internal standard approach. The method had a total coefficient of variation of 99.9%. Milyang 23 showed slightly higher degree of gelatinization than Akibare during cooking at 100℃. Both rice was completely gelatinized after 20 minute cooking.