High dispersibility and stability of carbon black particles in acrylonitrile-butadiene rubber (NBR) matrix were obtained by polymer grafting, and electrical resistivities of its thin layers were examined. First a polymer grafted carbon black was synthesized by the reaction with a polymer containing reactive group in the molecular unit. Then, the polymer grafted carbon black was dispersed into NBR, and its thin layers were prepared on glass substrates by spin coating for electrical measurements. The electrical resistivities of thin NBR layers which contained the polymer grafted carbon blacks showed smooth changes with carbon black concentration. The electrical resistivity of the layer with the polymer grafted carbon black increased smoothly with an increase in temperature. The relationship between the electrical properties of the layers and carbon black dispersion in the layer will be discussed. It is concluded that the polymer grafted carbon black can be expected to be a promising material for thin film resistors and conducting polymers.