A synthetic layered alkali silicate, magadiite, and a natural montmorillite were found to concentrate indium(III) ion from aqueous solution by ion exchange reactions. The adsorption was examined by the reaction between silicates and aqueous solution of indium(III) chloride of different concentration at room temperature for 10 min. The adsorption isotherms were H type, indicating strong interactions between the silicates and indium(III) ion. The maximum adsorbed indium(III) amount for magadiite was quite high, ca. 0.70 mmol/g silicate, which corresponded to 96% of the ideal cation exchange capacity of magadiite derived from the chemical formula of Na2Si14O29. In addition, the selectivity of the indium was very high, and efficient adsorption of indium was observed from the sodium chloride solutions and the solutions containing zinc, nickel, and copper. The large adsorption capacity, high selectivity of indium, and short reaction time (10 min at room temperature) make the adsorption on magadiite useful for the concentration of indium(III) ion from aqueous environments.