A rubber composition contains a diene rubber including a styrene-butadiene copolymer component including a styrene-butadiene copolymer and a reinforcing filler. (1) The bonded styrene content is from 5 to 50 wt. %. (2) The total amount of styrene of an ozone decomposed component S1 including one styrene-derived unit and an ozone decomposed component S1V1 including one styrene-derived unit and one 1,2-bonded butadiene-derived unit is less than 80 wt. % of the amount of bonded styrene. The total amount of styrene of the decomposed component S1V1 is not less than 10 wt. % of the amount of bonded styrene. (3) The integrated intensity of an ozone decomposed component S1V2 including one styrene-derived unit and two 1,2-bonded butadiene-derived units is less than 15% of the area intensity of all decomposed components including styrene-derived units. (4) The vinyl content of a butadiene portion is not less than 20% and less than 50%.