A rubber composition includes .alpha.,.beta.-ethylenically unsaturated nitrile-conjugated diene copolymer rubber (A), .alpha.,.beta.-ethylenically unsaturated nitrile-conjugated diene copolymer rubber (B), ethylene-.alpha.-olefin copolymer rubber (C), and a graft copolymer (D). The graft copolymer (D) is obtained by performing graft copolymerization on a mixture of an aromatic vinyl compound and an .alpha.,.beta.-ethylenically unsaturated nitrite monomer with an ethylene-propylene-unconjugated copolymer. A content of structure units of the ethylene-propylene-unconjugated copolymer is 20 to 70 wt %, a ratio of the graft copolymer (D) with respect to 100 parts by weight in total of said rubber (A), rubber (B) and rubber (C) is 1 to 30 parts by weight. A composition ratio of the rubber (A), rubber (B) and rubber (C) is rubber (A): 20 to 79 wt %, rubber (B): 1 to 30 wt %, and rubber (C): 20 to 50 wt %.