[Aim and scope] To promote sustainable timber and forest biomass utilization, technically feasible and economically viable availability should be estimated considering forest regeneration. Therefore, this study calculated incomes and expenditures such as silvicultural and harvesting as well as stumpage prices on the Japanese cedar, cypress, pine, and larch forests using the silvicultural prescriptions set based on the regional forest plans and operation systems set based on topographic conditions such as slope angles and height differences with GIS. [Methodology] This study acquired the forest GIS for private and communal forests from prefectures and national forests from the Forestry Agency of Japan. Then, this study estimated the availability of unused materials for woody biomass power generation plants under operation with FIT at the end of June 2020 as the supply potential from the profitable subcompartments. [Novelty] Most of existing studies estimated them as a unit of municipality or a 1 km mesh whereas the present study estimated them as a subcompartment, which was an actual forest management unit. [Results] Supply potentials of used and unused materials were estimated at 65,490,336 m³/year and 13,098,067 m³/year, respectively whereas those availabilities were estimated at 31,080,672 m³/year and 6,216,134 m³/year respectively. Therefore, the rate of the availabilities to the supply potentials was 47.5%. Furthermore, the rate of the availabilities to the demands was 71.6%. Considering the subsidy rate of 100% to secure the reforestations, the availabilities met the demands in Japan as a whole. [Conclusions] The present study imply that subsidies play an essential role in the profitability of forestry operations as well as the supply of timber and forest biomass resources in Japan. The results obtained in the present study can contribute to the effective utilization of forest resources under sustainable forest management.