Life Cycle Assessment (LCA) is an environmental assessment method that has come into wide use. The LCA method has been used to assess the environmental impact of various products from domestic articles like plastic trays to large buildings. However, few LCA studies on domestic lumber have been conducted because of regianal and other differences in forestry methods, distribution, etc. In this study, to obtain basic knowledge on the environmental impact of sugi lumber products, we investigated energy consumption, amount of waste, and volume of product in processes from felling to sawmilling. From the obtained data, emissions of environmental load substances were quantified and evaluated by LCA. The main results obtained are as follow: CO2, CO, NOx, and SO2 were emitted in large quantities from the sawmill subprocess. This is probably due to the large electricity consumption of sawmill equipment. The amount of CO2 emissions depends on the yield of the sawmil and the distance from market of the sawmill. Therefore, effective means to reduce the CO2 emissions were suggested as follow: the sawmill equipment can be rationalized to improve the yield in sawmill subprocess, and the sawmilling line can be made more highly effective; in addition, it is important to plan construction of sawmills so that the distance from the sawmill to the market will be shortest. Global warming and acidfication comprise almost the entile result of the impact assessment of both sawmills. The substances that contributed to global warming and acidification were CO2, NOx, and SO2, and CH4, and each substances was emitted most in the sawmill subprocess. Overall, this study showed that the sawmill subprocess has the greatest role in the environmental load of lumber products.