It is intended to provide a complex of lactoferrin with a nonpeptidic hydrophilic high-molecule, which as a lowered antigenicity and a pepsin-resistance imparted thereto, shows a prolonged life in vivo and has a high clinical usefulness, and a method of producing the same. Moreover, it is intended to provide a lactoferrin complex, which sustains the biological activity of natural lactoferrin at a specific level, shows a significantly prolonged life in vivo and is superior in clinical usefulness to natural lactoferrin, and a method of producing the same. As one embodiment, a biologically active complex of lactoferrin with a branched nonpeptidic hydrophilic high-molecule can be presented.
