Adsorptive removal of fluoride ions from water by hydroxyapatite (HAp) prepared from spent mold gypsum for producing ceramics was investigated. The HAp exhibited high adsorption of fluoride ions at neutral pH. Various HAps with different molar ratios of calcium to phosphorus prepared from spent mold gypsum were compared with commercially available HAp for column chromatography. It was found that the HAp prepared from spent mold gypsum effectively adsorbs fluoride ion over a wider pH range, up to the weakly alkaline region, than commercially available HAp, and that the adsorption is not affected by the molar ratio of calcium to phosphorus. A column packed with the HAp prepared from spent mold gypsum was tested for removal of excess fluoride ions from hot-spring water. Fluoride ions were selectively adsorbed from among other anionic and cationic species present and their concentration was successfully lowered below the environmental standard value.