The effectiveness of electromagnetic interference (EMI) shielding was measured for poly vinylidene fluoride (PVDF) coating materials containing carbon nanofibers. When the thickness of carbon nanofibers filled PVDF coating materials varied from 25 to 100 μm, the electrical conductivity of coating materials was almost constant around 2.0 S/cm except for the case of 25 μm. Although the electrical conductivity should not change with the thickness of coating, the lower value with the thinner thickness could be related to the lack of uniformity at the lower thickness range. The specific surface area and electrical conductivity of filler were important factors for the shielding effectiveness (SE) of the coating materials. In order to apply carbon nanofibers as EMI shielding materials, large specific surface area and high electrical conductivity were desirable. The SE of the coating material showed a high value with the mild heat treatment at 1100 ℃ for 1 h and was proportional to the electrical conductivity of the coating materials.