The object of this study was to investigate the effects of rice particle size on the physicochemical properties of beef-rice porridge. The pH of beef-rice porridge was decreased as compared to that of the control, while the redness of beef porridge increased according to rice particle size. The viscosity of flour in the beef-rice porridge was the highest among three porridges, at $40^{circ}C$. The protein content of beef-rice porridge was increased 3-fold over that of rice porridges. The total amino acid content of the beef-rice porridge was 3071.2 mg/100 g, and that of rice porridge was 1147.5 mg/100 g. As compared to rice porridge, the maximum amounts of the amino acids Lys and Thr were increased beef-rice porridge. Sensory evaluation results showed that the beef-rice porridge with a particle size half that of rice had the highest scores in color, taste, texture, and overall preference. Based on these results, it is suggested that beef-rice porridge with a particle size half (0.7-2.5 mm) that of rice has optimal quality in terms of both physicochemical and sensory properties.