To obtain the subject composition having excellent thermal conductivity and electrical insulation, easily moldable to give a molded article having excellent surface smoothness, producible at a relatively low cost and usable also as a magnetic material by compounding an elastomer with a ferrite.

The objective composition is produced by compounding (A) an elastomer with (B) a ferrite. The component A is preferably an elastic polymeric material such as various rubbers, e.g. a silicone rubber. The component B is e.g. soft magnetic ferrite or hard magnetic ferrite. The component B may have an arbitrary form such as sphere, fiber or indefinite form and is especially preferably spherical form. The component B is preferably surface-treated with a silane coupling agent to improve the miscibility of the silicone rubber with a heat-conductive filler and obtain a homogeneous molded article.