A method for preparing a culture mixture of a soybean-rice bran mixture, Aspergillus oryzae and Bacillus subtilis is provided to overcome the problem of impossible symbiosis of Aspergillus oryzae and Bacillus subtilis in the same culture medium by culturing them in sequence. A method for processing the culture mixture is provided to secure the storage property and the processability by hot-wind drying or freeze-drying. A method for preparing a mixture culture material of a soybean-rice bran mixture, Aspergillus oryzae and Bacillus subtilis comprises the steps of: (a) adding 10-20 wt.% of cooked rice bran prepared by cooking the rice bran having the moisture of 40-50 wt.% at a temperature of 100 deg.C for 20-30 minutes to cooked soybean prepared by cooking the soybean at a temperature of 121±1 deg.C for 20-30 minutes to prepare a cooked soybean-rice mixture; (b) inoculating 0.6-0.8 wt.% of Aspergillus oryzae into the cooked soybean-rice mixture and culturing it at a temperature of 30-33 deg.C for 12-15 hours
