A rubber composition for tire treads is obtained by blending, per 100 parts by mass of a diene rubber, 5 to 150 parts by mass of silica and 0.5 to 20 parts by mass of a silicone oligomer represented by the following siloxane average formula (1): (X)a(Y)b(R1)c(R2)dSiO(4-a-b-c-d)/2 (wherein X is a mercapto group-containing organic group; Y is a hydrolyzable group, R1 is a monovalent hydrocarbon group having from 4 to 10 carbon atoms, R2 is a monovalent hydrocarbon group having from 1 to 3 carbon atoms, 0