Mitsubishi Materials Corporation (MMC) initiated an exploration program in the northern part of the Hachimantai volcanic region in 1965. After the completion of the Ohnuma geothermal power station in 1974, a decision was reached to direct further exploration towards the Sumikawa geothermal field. The Sumikawa geothermal power station has been developed jointly by MMC, which is in charge of the steam supply, and Tohoku Electric Power Company Inc., which is in charge of generating electricity, and was completed in 1995. It has been producing electricity at range of 42 MWe and 50 MWe. This paper mainly presents a review of the developing history, development strategy and reservoir behavior of the Sumikawa geothermal field. Furthermore, we would like to show some subjects in order to promote a future geothermal development.