To provide a complex of a non-peptide hydrophilic polymer and lactoferrin that is reduced in antigenicity, is endowed with pepsin resistance and has a prolonged in-vivo lifetime and therefore is highly clinically useful and a manufacturing method thereof, and to provide a lactoferrin complex that retains a certain rate of bioactivities of natural lactoferrin, has a significantly prolonged in-vivo lifetime and is more excellent in clinical usefulness than natural lactoferrin, a manufacturing method thereof, and the like.

A biologically active complex of a branched non-peptide hydrophilic polymer with lactoferrin is provided. The complex retains binding performances to iron inherent in lactoferrin and therefore retains important bioactivities of lactoferrin resulting from at least iron-binding performances. The complex exhibits resistance to proteases such as pepsin, trypsin or the like owing to the bound branched non-peptide hydrophilic polymer, and therefore has a long in-vivo lifetime and exhibits bioactivities in the body for long hours.