Disclosed are a targeting magnetic nanosphere preparation capable of diagnosing and treating tumors in mammals and a method of manufacturing the same. The smart magnetic nanosphere preparation contains magnetic nano-sized iron oxide nanoparticles, which can be detected by magnetic resonance imaging (MRI), as a core material. The core material is encapsulated in a size of tens to hundreds of nanometers allowing particles to penetrate into deep areas of biological tissues using a biodegradable polymer having high affinity for biological tissues. The formed capsules are surface-modified with an antibody specific to a specific tumor. The smart magnetic nanosphere preparation can effectively diagnose tumors, as well as treat tumors because it has an antibody to a specific tumor.