PURPOSE: To provide a tread rubber composition having rolling resistance substantially reduced without damaging friction resistance on a wet road surface, by incorporating a specific, amount of high-vinyl polybutadiene rubber containing a 1,2- bond unit above a specific amount.

CONSTITUTION: 80W100pts.wt. high-vinyl polybutadiene rubber containing a 1,2- bond unit in an amount of 65% or more is blended with 20W0pts.wt. other rubber component, such as polyisobutylene rubber, e.g. natural rubber, synthetic polyisobutylene rubber or styrene-butadiene rubber. Further, it is necessary that the intrinsic viscosity[y]at 30°C of a high-vinyl polybutadiene rubber solution in toluene is 2.0 or more. Rolling resistance is improved with the increase of the intrinisc viscosity[y]. In particular, with an instrinsc viscosity of 2.0 or more, the titled composition has rolling resistance supeiror to natural rubber having the most excellent rolling resistance so far.