The present invention relates to a superparamagnetic gold nanoparticle cluster-protein nanoparticle fusion body for magnetic resonance imaging and magnetic thermotherapy. According to the present invention, a superparamagnetic gold nanoparticle cluster-protein nanoparticle fusion body which has target directionality and a high density of ultrafine gold nanoparticles uniformly coupled to the surface of protein nanoparticles can be fabricated with neither a separate surface stabilization process nor a separate target directionality conferring process. Hence, the superparamagnetic gold nanoparticle cluster-protein nanoparticle fusion body according to the present invention is superior to conventional gold nanoparticles in terms of biocompatibility and has excellent target directionality as well as being identified to have a temperature elevation potential in an alternating magnetic field and a functionality as a T2-MRI contrast medium thanks to the superparamagnetism property of the ultrafine gold nanoparticles. Therefore, the superparamagnetic gold nanoparticle cluster-protein nanoparticle fusion body according to the present invention can be utilized as a core technology in the fields of magnetic thermotherapy and magnetic resonance imaging contrast media.
