The present invention provides a rubber composition which has closed cells and comprises (A) at least one rubber component selected from natural rubber and diene-based synthetic rubbers, (B) silica in an amount of 10 to 150 parts by mass based on 100 parts by mass of the rubber component, (C) an organic fiber in an amount of 0.02 to 20 parts by mass based on 100 parts by mass of the rubber component and (D) a silane coupling agent represented by following general formula (I): ##STR00001## in an amount of 1 to 30% by mass based on the amount by mass of silica of Component (B), exhibits excellent workability in processing the rubber and can provide a tire exhibiting excellent performance of braking and driving on road surfaces having ice and snow (excellent performance on ice) and excellent abrasion resistance; and a pneumatic tire which is obtained by using the rubber composition for a tread and exhibits the performance described above.