To provide a rubber composition for use in tire inner liners which simultaneously satisfies both the air-permeability resistance and the flexural fatigue resistance, and to provide a pneumatic tire using it.

The rubber composition for use in tire inner liners, comprising a blend of 100 pts.mass of a rubber component (but, the rubber component accounts for 50 pts.mass or more of a butyl-based rubber), 5-25 pts.mass of an oil-extended china clay, 10 pts.mass or more of an inorganic filler and 30 pts.mass or more of a carbon black, is characterized in that the sum total blending quantity of the above oil-extended china clay, inorganic filler and carbon black is 45-100 pts.mass. The pneumatic tire uses the rubber composition as the inner liner.