The present invention discloses a magnetic nanomedicine for inhibiting/treating human prostate cancer, which comprises a core containing a magnetic particle having a diameter of less than 10 nm; a shell made of a carboxylated polyaniline and encapsulating the core; and a medicine covalently linked to the shell and able to inhibit/treat prostate cancer. The magnetic nanomedicine of the present invention not only has superior thermal stability and but also has water solubility higher than that of the conventional anti-prostate cancer medicine. Further, the magnetic nanomedicine of the present invention can be magnetically conducted to the cancer area to increase the local concentration of medicine and enhance the therapeutic effect.