A nitrile rubber composition comprising 1,000 to 1,200 parts by weight of a magnetic powder having a compressed density of 3.4 to 3.7, based on 100 parts by weight of nitrile rubber, hydrogenated nitrile rubber, or a blend rubber thereof, the rubber having a Mooney viscosity ML1+4 (100° C.) of 20 to 50. The nitrile rubber composition that does not undergo deterioration of roll processability and adhesion to molds during product vulcanization even when a large amount (e.g., 1,000 parts by weight or more) of magnetic powder is added based on 100 parts by weight of nitrile rubber, hydrogenated nitrile rubber, or a blend rubber thereof.