The authors investigated the spatial variation of topsoil salinity in rice fields damaged by the 2011 Tohoku Earthquake Tsunami. Four study locations were selected from the alluvial plain of the lower Natori River in the Sendai Plain. The results suggest that salinity is lower in inland areas but increases in coastal areas because of geographical factors such as distance from the coastline, artificial constructions, microrelief, and altitude. For about six months after the tsunami, salinity decreased remarkably, but not in seaside locations. For this reason, it was difficult to distinguish the fluctuation caused by sampling methods and the temporal variation.