In recent years, submarine groundwater discharge (SGD) have received considerable attention in hydrology and oceanography. Radon-222 (222Rn) is a useful tracer to detect SGD because 222Rn in groundwater has extremely high concentration compared with surface waters. In Japanese coasts, many researches have been done SGD observations using 222Rn tracer techniques. If we compiled 222Rn data from many coasts with different environmental condition, we can get generality related environmental parameters to SGD. Therefore, objectives of this study are to compile the existing observed data in Japanese coasts and to evaluate environmental parameters concerning the regional difference in 222Rn activities. Firstly, we consolidated 222Rn data in coastal waters at 10 sites from the northern part to the southern part of Japan. We also prepared environmental parameters in each watershed such as precipitation, geological data and geomorphological characteristics to examine and effect of driving forces on the regional difference of 222Rn activity. In this presentation, we will show the regional difference of 222Rn activities in Japanese coasts and statistical analysis results of relationship between compiled 222Rn data and environmental parameters.