PURPOSE: A crosslinkable rubber composition, containing an unsaturated nitrile- conjugated diene copolymeric rubber, ethylene-propylene copolymeric rubber and an olefinic high polymeric material, and having oil and ozone resistance higher than that of chloroprene rubber.

CONSTITUTION: A composition prepared by incorporating a mixture of 100pts.wt. total of 90W50pts.wt. unsaturated nitrile-conjugated diene copolymeric rubber and 10W50pts.wt. ethylene-propylene copolymeric rubber with at least 1pt.wt., preferably 4 pts.wt. or more, olefinic high polymeric material with a vulcanizing system. The olefinic high polymeric material is uniformly mixed with the rubber component in the mixture. In order to improve the mechanical strength of a vulcanized article, the ethylene-propylene copolymeric rubber is previously kneaded with a small amount of an olefinic high polymeric material and a small amount of carbon black at a temperature of the melting point or softening point of the high polymeric material or above and then kneaded with the unsaturated nitrile-conjugated diene copolymeric rubber.