A new and simple method for synthesizing graphitic carbon-coated magnetic-metal (Co, Ni and Fe) nanoparticles has been reported. The mixture of metal and diamond nanoparticles was just annealed at 1700 degrees C in vacuum. The annealed samples were studied by high-resolution transmission electron microscopy, selected-area electron diffraction and X-ray diffraction. These analyses revealed that magnetic-metal particles are coated with uniform graphitic layers several nanometers in thickness.