Toxic inorganic anions (arsenate, chromate, fluoride, selenate, and selenite) adsorptions, and the concomitant proton consumptions together with the sorptions were investigated using an allophanic andisol in Japan. The investigations of nitrate and phosphate adsorptions were also carried out as comparative data. The adsorption isotherm of each anion was made at suspension pH 5.0, analysed with the simple Langmiur equation. Judging from the estimated adsorption maximum, the order of adsorption affinity to the andisol was, fluoride≫phosphate >selenite>arsenate≫selenate≧chromate≧nitrate. The concomitant proton consumptions were not observed in the adsorptions of selenate, chromate and nitrate. The order of the concomitant proton consumptions together with the adsorptions was fluoride≫phosphate>selenite> arsenate. Our results confirm that fluoride, phosphate, selenite, and arsenate are adsorbed on the soil particle surfaces by ligand exchanges, forming the inner-sphere complexes, and that selenate, chromate and nitrate are attracted as an ion pair, outer-sphere surface complexes with water molecules between the anion ions and the soil surface.