The anthropogenic pollution by rare earth elements (REEs) in river water around urban area in Japan was investigated based on multielement determination by ICP-MS after solid-phase extraction using a chelating resin. As a result, the potential anthropogenic pollution by Eu as well as Gd was observed for the river water in the Sakai River, which flows across some urban area from Machida-shi, Tokyo, to Fujisawa-shi, Kanagawa. In particular, the potential anthropogenic pollution due to Eu in river water was found for the first time in the world.