The feature of the Koji -container made of Japanese ceder was examined by using an automatic kojimaking apparatus. Steamed rice in wooden containers was kept at 35°C under humidity of 85 or 50% for 24 hr, and the amounts of moisture adsorbed in the wood and diffused into air were estimated separately from the weight decrease. The decreased moisture was 1. 7 and 1. 5 times as much, respectively, as the one in containers of other materials under 85 and 50% humidity, respectively. Results indicated that the desiccation proceeds even in humid air. Similar results were obtained with steamed rice inculated with koji mold, but the growth of the mold was more active in containers of other materials than in wooden containers. When he quality of the koji made in wooden containers was evaluated by enzyme activities or shouka-hou (a method proposed by the authors), no marked difference was observed among the ones made in containers of other materials. But its color was whiter than the others, and the mold propagation was in the state of Tsukihaze (deep penetration of mycelia into rice grains rather than propagation on grain surface).