Rubber composition for sidewall and pneumatic tire using the same

A rubber composition for sidewall which can prevent color change to brown and has sufficient ozone resistance and improved low heat build-up characteristics, and a pneumatic tire having sidewall comprising the rubber composition. The rubber composition comprises 5 to 150 parts by weight of carbon black having nitrogen adsorption specific surface area of 70 to 300 m/g and 5 to 100 parts by weight of calcium carbonate based on 100 parts by weight of a rubber component comprising 20 to 70 % by weight of a natural rubber and 30 to 80 % by weight of a synthetic diene rubber.