Abstract: Provided is a poly-?-glutamic acid derivative having appropriately controlled hydrophilicity, which can be processed into a form of fine particles. Provided is a PGA derivative in a form of fine particles having a particle diameter of 50 to 1,000 nm, which is obtained by introducing cholesterol into poly-?-glutamic acid (PGA). Thus, the PGA particles can be mixed with various biological materials (e.g., medicament) so as to be used in various applications in the field of biotechnology. Specifically, it can be used as a carrier of a medicament, or the like. Further, it is also made possible to use PGA in various applications in the field of nanotechnology that is studied in recent years.