This paper proposes the use of inter-regional input-output model for water accounts (IRIOWater), which combines inter-regional input-output model and water accounts system, as a tool to evaluate water demand and water-policy impacts among each industrial sector in Shikoku region of Japan. This IRIO-Water model which combines a descriptive device and an analytical tool, is enumerated by combining three regions as (1) upper Shikoku, (2) lower Shikoku, and (3) the rest of Japan under conditions of rainfall pattern, geographical area, and inter-regional trade of each region. The calculation results of water demand are compared among each industrial sector with impacts from implementation of governmental policies such as 3Rs policy (reduce-reuse-recycle). The results in this paper indicated that IRIO-Water