The effects of the concentration of citric acid in the steeping water on the growth of white koji fungus and the production of hydrolytic-enzymes and citric acid during koji production in barley shochu brewing, in which barley was steeped in a restricted amount of water (RW method), were investigated. Addition of 0.25% (w/v steeping water) citric acid to the steeping water resulted in acceleration of the production of them. The amount of citric acid in a 30 h koji produced by the RW method using the steeping water containing 0.25% citric acid was almost the same as that of a control after incubation for 44 h. These results suggest that the time for shochu-koji production can be shortened.