Thirty mael Sprague Dawley rats of 3 weeks of age were adopted to investigate changes in nutritive quality of the traditional, fermented soybean foods, Meju and Chungkugjang prepared by culturing with Aspergillus oryzae and the rice straw, respectively. The levels of each dietary protein were set at 10% . The effect of supplementation of fermented soybean on the rat diet was evaluated by measuring growth rate, feed efficiency. weight of the pancreas and biological values, such as NPU, PER and NPR on day 10. After incubation of soybean with Aspergilllus oryzae and the rice straw, the contents of crude protein, crude fat and crude ash were increased, but the levels of crude fiber and nitrogen-free extract were reduced. The amounts of feed intake, body weight gain an feed efficiency were greater for the rats fed dietscontaining heated unfermented soybeans or Meju compared to rats fed the diet containing raw soybeans. Pancreating enlargement was observed in the rats fed diets containing raw soybeans. The values of NPR and PER in rats fed diets containing Meju and Chungkugjang were significantly higher than those of rats fed diets containing raw soybeans. The values of NPU in rats fed diets containing raw soybans, heated unfermeted soybeans. Meju and Chungkugjang were 39.40%, 40.60%, 45.00% and 46.205, respectively, demonstrating no significant differences.