Inyu, like soy sauce, is a traditionally fermented condiment in Taiwan and made by black beans. It has special properties in flavors and qualities, however, its market share is lower than soy sauce made by automatic koji-making method due to limitation in production scale and labor cost. In this study, the optimum soaking and cooking conditions were determined by response surface methodology (RSM), and the mechanically koji-making method was investigated to evaluate the feasibility of koji-making method for Inyu as compared to the traditional method. According to superimposed plots of enzyme susceptibility and enzyme activity, cooking at 132 for 23min after soaking with water at room temperature for 4 hr was the optimum cooking conditions of black beans for making Inyu. The water content and hardness of the cooked black beans were 50.7% and 61.6g, respectively. The proper water content and protein denaturation were required for growth of koji mold and protein hydrolysis by enzymes produced during koji making. The thickness of cooked black beans was related to water loss during mechanical koji-making. Water content of the koji with the 6-cm thickness was too low to be available for koji mold and only low enzyme activities were obtained. On the other hand, enzyme activities for the koji thickness at 12-18cm were higher than that from traditionally koji-making method. The activities of acid-, neutral-, alkaline-protease and amylase were 423, 543, 525, and 1127 units/g dry koji for the koji thickness at 12cm. Faster growth and the mycelium stretched to cotyledon of the black beans were observed for the koji mold by mechanical koji-making method than that of traditionally method. Therefore, koji-making through an automatic process by mechanized facilities was feasible in manufacturing of Inyu.