To obtain a decomposition product of bone tissue excellent in absorption into a living body and fixing to bone tissue, and useful for preventing or curing osteoporosis by treating natural bone with electrodialysis to convert it into a decomposition product of bone tissue substantially free from protein molecules which constitute the natural bone, while containing natural bone-derived amino acids or the like.

Natural bone is converted into a decomposition product of bone tissue substantially free from protein molecules which constitute the natural bone, while containing amino acids and soluble minerals derived from the natural bone by treating the natural bone with electrodialysis. This decomposition product of bone tissue is obtained, for example, by crushing bovine femoral bone or the like, washing the crushed bone with hot water and a sodium hydroxide solution to completely remove fat-and-oil, excess connective tissue or the like of the bone, charging the treated crushed bone into an anode tank of an electrolyzer in which an anode plate and a cathode plate separated with a cation-exchanger membrane are placed oppositely, charging the electrodes with electricity, recovering a matrix component formed on the anode tank side by filtration, transferring the recovered component to the cathode tank side, charging the electrodes with electricity, mixing the decomposition liquids of both the tanks, emulsifying the mixture, and drying it.