On the other hand, growing stock of Japanese forest is 5 billion m³ or more, but the unused thinnings are scarcely utilized. When 0.1 billion m³/year woods in this growth are used for woody biomass fuels, that potential energy would be very large as 60 TWh/year. For the realization of this potential energy, the significant cost reduction is necessary, because the current total wood production costs from the planting to the final cutting are very high in Japan. For the competitive international woody biomass energy costs, Japanese current wood total production costs are required to reduce to about 1/5. About the final cutting costs in the forest with gradual slope of less than 20°, it was calculated the result which can reduce to the same extent as international costs, by promoting the mechanization of harvesting and securing the sustainable unit business volume which is the forest area of about 10,000 ha /50 years.
　In the future, the silvicultural cost reduction and selecting the suitable forestry machines which have being developed recently for steep terrain of more than 30°slope will be studied. And some working systems that are suitable for the each area will be proposed. For the sustainable management of forestry, the consolidation of the working area of about 10,000 ha unit and the establishment of the supply and demand system of wood are also required. Then the comprehensive improvement review of Japanese forestry will be conducted.