A rubber composition comprising: (A) at least one copolymer ingredient selected from the group consisting of ethylene/&agr;-olefin copolymer rubber and ethylene/&agr;-olefin/unconjugated diene copolymer rubber, (B) nickel diisobutyldithiocarbamate, and (C) carbon black, and not containing any compound having zinc; a vulcanized rubber composition obtained by vulcanizing the rubber composition; and a heat-resistant rubber product using the vulcanized rubber composition.