Disclosed is a rubber composition having a high storage modulus (G’) and a low loss tangent (tan δ). Specifically disclosed is a rubber composition characterized by containing 2-60 parts by mass of a low molecular-weight aromatic vinyl compound-conjugated diene compound copolymer (B) having at least one functional group per 100 parts by mass of a rubber component (A). The rubber component (A) is composed of at least one rubber selected from natural rubbers and synthetic diene rubbers. The low molecular-weight aromatic vinyl compound-conjugated diene compound (B) is characterized in that the aromatic vinyl compound content is 5-80% by mass, the vinyl bond content in the conjugated diene compound unit is 5-80% by mass, and the weight average molecular weight in terms of polystyrene as determined by gel permeation chromatography is 5,000-500,000.