Abstract: Rubber composition for a base tread, which is obtainable by blending, per 100 parts by weight of a rubber component, 30 to 55% by weight of a carbon black having an iodine adsorption value of from 40 to 100 g/kg, wherein the rubber component comprises (A) 20 to 55% by weight of a star shaped solution-polymerized butadiene rubber and (B) 45 to 80% by weight of a natural rubber or a natural rubber containing a diene rubber other than a star shaped solution-polymerized rubber in an amount of not more than 50% by weight. When using the above-mentioned rubber composition for the base tread of a base portion of a tread having a cap/base two-layer structure, it is possible to save fuel consumption of the tire because of small deformation and uniform shape.