Korean Yung-il bentonite was treated with potassium chloride, zinc chloride, calcium chloride, ferric chloride, or chromic chloride solutions respectively varying their concentration, treating temperature and treating time. The adsorbabilities of methylene blue on these pretreated bentonite were investigated. In the case of treatment with potassium chloride solution, the improvement of the adsorbahility of methylene blue on the products was observed, and in the best result the adsorbability was 1.6 times better than that on the original bentonite. With zinc chloride solution, the optimum adsorbability was a value of 1.7 times better than that on the original bentonite. With ferric chloride, chromic chloride or calcium chloride solution, slight improvement of the adsorbability was observed.