To provide a rubber composition comprising an isomonoolefin-p- alkylstyrene copolymer which is greatly improved with respect to S-S characteristics and has excellent tensile strength.

This composition comprises 100 pts.wt. of a halogenated copolymer of a 4-7C isomonoolefin and a p-alkyl styrene, 0.5 to 10 pts.wt. of a compound having, in one molecule thereof, two or more of chemical structure units represented by the formula, and 1 to 10 pts.wt. of at least one crosslinking component selected from among zinc salts of 12-22C saturated and unsaturated fatty acids and zinc oxide.