A composition for a sealing material which comprise a rubber component comprising copolymer rubbers of ethylene, α-olefin having 3 or more carbon atoms and unconjugated diene, a vulcanizing agent and a blowing agent, wherein the copolymer rubber consists of copolymer rubber A and copolymer rubber B, the copolymer rubber A being derived from ethylene, α-olefin having 3 or more carbon atoms and 3 to 5% by mass of unconjugated diene, and the copolymer rubber B being derived from ethylene, α-olefin having 3 or more carbon atoms and 9 to 15% by mass unconjugated diene, and a mass ratio (copolymer rubber B/copolymer rubber A) of the copolymer rubber B to the copolymer A is in the range of 1/99 to 50/50, and a sealing material composed of a vulcanized foam of the composition.