The adsorption behavior of Cs+ with the modified mica was investigated in aqueous suspension, quantitatively. Phlogopite was used as typical mica. We newly found out that phlogopite treated with BaCl2 for a short period (2 h) exhibits ability to adsorb Cs+, equivalent to phlogopite treated with a conventional reagent such as sodium tetraphenylborate (NaTPB). Since BaCl2 is a much cheaper reagent than NaTPB and the treatment period is very short, this finding would be valuable to provide a practical method to remove radioactive Cs+ from the environment.