A biologically active complex of lactoferrin with a branched non-peptide hydrophilic polymer, one example of which is represented by the following formula [I]:
LF-[X-Lp-R—(Yp-POLY)q]n [I]
Wherein LF is lactoferrin, X is a linkage generated by reaction of functional groups, L is a linker, R is an aliphatic hydrocarbon group having at least 3 carbon atoms, Y is a heteroatom linkage, POLY is a non-peptide hydrophilic polymer, p is 0 or 1, q is an integer of 2 to 10, and n is an integer of 1 to 10.