To provide a new and useful ethylene.α-olefin.triene copolymer rubber having high vulcanization rate and excellent scorch stability and shape-retaining property, a crosslinkable rubber composition containing the rubber, a molded and crosslinked rubber article for sealing produced by crosslinking the above crosslinkable composition and a process for producing the rubber.

The ethylene.α-olefin.triene copolymer rubber is composed of a structural unit derived from ethylene, a structural unit derived from a 3-20C α-olefin and a structural unit derived from a triene compound of formula (1). The molar ratio of the structural unit derived from ethylene to the structural unit derived from a 3-20C α-olefin, the intrinsic viscosity measured in decalin at 135°C, the content of the structural unit derived from the triene compound, etc., are adjusted to fall within respectively specific ranges.