Disclosed is a rubber composition characterized by having a closed cell and containing, per 100 parts by mass of at least one rubber component (A) selected from natural rubbers and diene synthetic rubbers, 10-150 parts by mass of silica (B), 0.02-20 parts by mass of an organic fiber (C), and 1-30% by mass of a silane coupling agent (D) represented by the general formula (I) below relative to the silica component (B). This rubber composition is excellent in workability during rubber processing and enables to obtain a pneumatic tire having excellent braking/driving performance on iced and snowedroad surfaces (on-ice performance) and good wear resistance. Also disclosed is a pneumatic tire exhibiting such performances, which uses the rubber composition in the tread.