This paper is to revisit the issue that the korean rice is becoming an inferior good. Theoretically a demand function stars from the consumer's utility maximization problem. Thus it must satisfy homogeneity, adding-up condition, symmetry, and non-negativity. The AIDS model is the one of empirical models satisfying them. It is an ideal model which estimates all commodities' demand function in the market. The weak separability of utility and two-stage budgeting is assumed to estimate a rice demand function with AIDS model. As result, AIDS model is composed of four commodities of rice, meat, wheat and non-living food.