Abstract:The formation of Kanto Plain around Tokyo Bay,Japan,is a sediment in the oceanic environment through several hundred thousand years or even million years¢ geological activity. Under this geological activity,Ocean Plankton was transformed into high quality water soluble natural gas and medicine iodine. Since 1930s,there were gas production activities near Tokyo. Large-scale production of gas and iodine in Kujyukuri area started from 1956. Production was conducted through withdrawal of groundwater from the depth of 500 to 2 000 m. Land subsidence was found since 1960s and large-scale land subsidence surveying was started in 1969. During past 35 years,the maximum accumulated subsidence was 0.85 m and subsided area was 800 km2. The coastal line of Kujyukuri backed off 20–50 m from its position in 1960s. In 2002,there is about 20 mm subsidence per year yet. Finally this paper describes South Kanto gas field and subsidence in Boso area. Discussion is made on the possible countermeasures to mitigate the subsidence:(1) recharge of some percentage of extracted volume of groundwater;(2) reduction of the withdrawal volume of groundwater. Through analysis of the structure of Kanto Geologic Basin,it is pointed out that reduction of the withdrawal volume of groundwater is more economic and effective than the other methods.