When grains of rice are heated and processed, the "water absorption process" that changes the grains from dry state to a state where gelatinization is possible, is an important step. We developed an innovative method in which a digital microscope with a polarizing lens is used to visualize the water absorption process in real time and to quantitatively evaluate it through image analysis. The mean brightness and the rate of increase of the projected area obtained from image analysis of rice grains that absorbed water at 10, 25, 40, and 55 degrees C presented a high degree of correlation with the change in water absorption rate by rice measured with an infrared moisture analyzer. The characteristics of the water absorption process were consistent with the results of nuclear magnetic resonance imaging.