A rubber composition containing a rubber component having an olefinic double bond, and an isobutylene polymer having a structural unit represented by the following formula (1) and a structural unit represented by the following formula (2), wherein the content of a low molecular weight substance whose molecular weight is 1000 or less in the isobutylene polymer is 5% by mass or less based on the total amount of the isobutylene polymer. [wherein X represents a divalent group, Y represents a substituted or unsubstituted alicyclic group having an unsaturated bond, and n represents 0 or 1.]
