[Problem] To provide a new useful technique using Bacillus subtilis. [Solution] A method for producing a compound bacteria fermentaion liquid such as Bacillus subtilis which is characterized in that production thereof involves performing a fermentation step for fermenting using Bacillus subtilis with a mushroom as a starting material, and an aqueous-solution extraction step for extracting an aqueous-solution component from the fermentation residue after the fermentation step. The present invention makes it possible to provide a new useful technique using Bacillus subtilis. In other words, this fermentation liquid produced by fermenting using a compound bacteria such as Bacillus subtilis with a mushroom as the starting material provides useful effects such as antibacterial activity and a psoriasis treatment effect.
