An object of the present invention is to provide a medical rubber composition having excellent non-elution characteristic and gas permeability. The present invention provides a medical rubber composition containing: (a) a butyl rubber, (b) a diene-based rubber containing polybutadiene, (c) a peroxide-based crosslinking agent, and (d) a co-crosslinking agent, wherein an amount of (b) the diene-based rubber in 100 parts by mass of the rubber component composed of (a) the butyl rubber and (b) the diene-based rubber is 15 parts by mass or more and 90 parts by mass or less, and a mass ratio ((d)/(c)) of (d) the co-crosslinking agent to (c) the peroxide-based crosslinking agent is 1.2 or more and 25 or less.