Sumitomo Osaka Cement Co., Ltd. (SOC) Kokura Mine and Mitsubishi Materials Corporation (MMC) Higashitani mine adjoiningly operate limestone mine at Hiraodai area in Kita-Kyusyu city, Fukuoka prefecture. MMC Higashitani mine need to replace underground facilities when bench down from current mining level in order to secure future minable deposit. SOC Kokura mine has undeveloped mining area between Higashitani mine, but cannot utilize their plenty minable deposit since there is no way to carry limestone to their cement plant because Kokura mine is located inland. In order to solve above issues, both mines started joint development project by focusing on the following five points. 1 Utilize the limestone deposit in SOC's undeveloped mining area and boundary area of both mines. 2 To plan production and shipping quantity for the purpose that all joint develop area can end mining at the same time. 3 Confirm content of installed facilities and investment cost between both companies and clarify way of cost allocation. 4 Ensure the safety operation and seek minimum cost. 5 Joint work to acquire necessary license/Approval and to solve social issue with local community. This joint project is not only aim to secure the limestone deposit, but also enable us to built long term supply system, obtain new customers and improve operating ratio by joint use of their facilities. And this approach would be the one of the ideal model of limestone mine.