A silicone rubber composition comprises:(A) an organopolysiloxane R.sub.a SiO.sub.(4-a)/2 having an average degree of polymerization of 3000 or greater, wherein R is a substituted or unsubstituted monovalent hydrocarbon group, and 0.0001-0.05 mol % of R is alkenyl; a is 1.95-2.05; and(B) a fine powder of hydrophobic silica, wherein the specific surface area is 50 m.sup.2 /g or greater, the silica surface includes hydrophobic groups f MesiO.sub.3/2 and Me.sub.2 SiO in a weight ratio (MeSiO.sub.3/2)/(Me.sub.2 SiO) or 5/95-95/5, and the total carbon content contained in the MeSiO.sub.3/2 and Me.sub.2 SiO groups account for 0.5 wt % of greater of the silica. A material obtained by hardening this rubber composition has desirable resistance to steam and LLC.