Removal of calcium and magnesium ions in a salt solution with the macroreticular chelating resin containing aminomethylphosphonic acid groups was investigated. The resin (RMT-P) exhibited high affinity for calcium and magnesium ions in a salt solution containing 200 g/dm3 of sodium chloride. In the column method, calcium and magnesium ions in a salt solution were preferentially absorbed on the RMT-P, when the salt solution containing 100 mg/dm3 of calcium or magnesium ion was passed through the RMT-P column at a space velocity of 15 h−1. The calcium and magnesium ions adsorbed were eluted by allowing 1 mol/dm3 hydrochloric acid to pass through the column. The recycle of adsorption and elution was found to be satisfactory.