A rubber composition comprising (a) a low molecular weight copolymer rubber
which is an ethylene/.alpha.-olefin/non-conjugated diene copolymer rubber
having a limiting viscosity [.eta.] of 0.4-1.6 dl/g measured in decalin at
135.degree. C., and an ethylene content of 40-60 wt % and (b) a high
molecular weight copolymer rubber which is an
ethylene/.alpha.-olefin/non-conjugated diene copolymer rubber having a
Mooney viscosity (ML.sub.1+4,100.degree. C.) of 60-150, an ethylene
content of 60-80 wt %, and an iodine number of 5-35, wherein the
difference between the iodine number of the low molecular weight copolymer
rubber (a) and the iodine number of the high molecular weight copolymer
rubber (b) is 5 or less and the ratio by weight of the low molecular
weight copolymer rubber (a) and the high molecular weight copolymer rubber
(b) is 50/50 to 80/20, the rubber composition having a Mooney viscosity
(ML.sub.1+4,100.degree. C.) of 20-50. The rubber composition exhibits
superior roll processability and extrusion processability, excellent
surface appearance and adhesiveness, can be processed easily, and produces
vulcanized rubber exhibiting excellent mechanical characteristics and good
low and high temperature properties.