An inorganic ion adsorbent represents by Formula (1) below, wherein in powder X-ray diffraction measurement using CuKα radiation, the diffraction intensity of tetragonal tin oxide is at least 3% relative to the diffraction intensity of antimony pentoxide (Sb2O5·2H2O), and the diffraction intensity of cubic antimony pentoxide is no greater than 40% relative to the diffraction intensity of antimony pentoxide (Sb2O5·2H2O), SnO2·aSb2O5·nH2O  (1) wherein in the Formula, a denotes a number that satisfies 0.2≦a≦4 and n denotes hydration number and is 0 or a positive number.