The present invention relates to a poly(organophosphazene)-superparamagnetic nanoparticle complex including a biodegradable and thermosensitive poly(organophosphazene) and a iron oxide (Fe3O4, Magnetite)-series ferrite superparamagnetic nanoparticle, a preparation method, and uses of carrying a physiologically-active material, a bio-material and a biomaterial for cancer hyperthermia. The iron oxide is used as a MRI contrast agent for T−2 and T2* weighted image, and the poly(organophosphazene) shows a sol-to-gel behavior depending upon the temperature change. The complex is a bound-type where the superparamagnetic ferrite nanoparticle is bonded to phosphazene-based polymer via hydrophobic binding, and a mixed-type where the superparamagnetic ferrite nanoparticle is physically mixed with the phosphazene-based polymer.