PROBLEM TO BE SOLVED: To provide complex nanofibers capable of protecting a medicine further firmly from an environment inside a digestive organ, and to provide a method for producing the same.SOLUTION: The complex nanofibers are formed by dispersing nanocapsules 14 including the medicine, into nanofibers composed of a polymer material. Preferably, the nanocapsule 14 is composed of a polyethylene glycol-cage-shaped silsesquioxane coupled body (hereafter referred to as PEG-POSS).