We investigated local structures around cadmium (Cd) sorbed on montmorillonite at various PH values by EXAFS (extend X-ray absorption fine structure). We found two sorption types, an outer-sphere complex and a surface precipitate. The outer-sphere complex was mainly formed at a lower PH which had an identical structure to aqueous Cd2+, while the surface precipitate was found at high PH which had a one-layer Cd-5(OH)(8)(NO3)(2) (H2O)(2)-like structure.