A rubber composition for tires, comprising: natural rubber; polybutadiene rubber; silica; and a silane coupling agent represented by the formula below, the natural rubber and the polybutadiene rubber being present in amounts of 20% by mass or more and 20% by mass or more, respectively, based on 100% by mass of a rubber component in the rubber composition, the silica being present in an amount of 50 parts by mass or more per 100 parts by mass of the rubber component, [Y 1 R 1 S x -] m [G 1 (R 2 SiX 1 X 1 X 1) a] n [G 2] o [R 3 Y 2] p wherein each G 1 independently represents a C1-C30 polyvalent hydrocarbon group containing a polysulfide group, represented by [(CH 2) b -] c R 4 [-(CH 2) d S x -] e; each G 2 independently represents a C1-C30 polyvalent hydrocarbon group containing a polysulfide group, represented by [(CH 2) b -] c R 5 [-(CH 2) d S x -] e; each of Y 1 and Y 2 independently represents a silyl group represented by -SiX 1 X 2 X 3, a hydrogen atom, a carboxyl group, or an ester group represented by -C(=O)OR 6; each X 1 independently represents -Cl, -Br, -OH, -OR 6, or R 6 C (=O)O-; each of X 2 and X 3 independently represents a hydrogen atom, R 6, X 1, or a -OSi-containing group formed by silanol condensation; each of R 1 and R 3 independently represents a C1-C20 divalent hydrocarbon group; each R 2 independently represents a linear hydrocarbon group represented by -(CH 2) f -; each R 4 independently represents a C1-C28 polyvalent hydrocarbon group or a heteroatom-containing C1-C27 polyvalent hydrocarbon group; each R 5 independently represents a C1-C28 polyvalent hydrocarbon group; R 6 represents a C1-C20 monovalent hydrocarbon group; and a, b, c, d, e, f, m, n, o, p, and x are independent from one another, each of a, c, and e represents a number of 1 to 3, each of b and d represents a number of 1 to 5, f represents a number of 0 to 5, each of m and p represents a number of 1 to 100, n represents a number of 1 to 15, o represents a number of 0 to 10, and x represents a number of 1 to 10. natural rubber; polybutadiene rubber; silica; and a silane coupling agent represented by the formula below, the natural rubber and the polybutadiene rubber being present in amounts of 20% by mass or more and 20% by mass or more, respectively, based on 100% by mass of a rubber component in the rubber composition, the silica being present in an amount of 50 parts by mass or more per 100 parts by mass of the rubber component, [Y 1 R 1 S x -] m [G 1 (R 2 SiX 1 X 1 X 1) a] n [G 2] o [R 3 Y 2] p wherein each G 1 independently represents a C1-C30 polyvalent hydrocarbon group containing a polysulfide group, represented by [(CH 2) b -] c R 4 [-(CH 2) d S x -] e; each G 2 independently represents a C1-C30 polyvalent hydrocarbon group containing a polysulfide group, represented by [(CH 2) b -] c R 5 [-(CH 2) d S x -] e; each of Y 1 and Y 2 independently represents a silyl group represented by -SiX 1 X 2 X 3, a hydrogen atom, a carboxyl group, or an ester group represented by -C(=O)OR 6; each X 1 independently represents -Cl, -Br, -OH, -OR 6, or R 6 C (=O)O-; each of X 2 and X 3 independently represents a hydrogen atom, R 6, X 1, or a -OSi-containing group formed by silanol condensation; each of R 1 and R 3 independently represents a C1-C20 divalent hydrocarbon group; each R 2 independently represents a linear hydrocarbon group represented by -(CH 2) f -; each R 4 independently represents a C1-C28 polyvalent hydrocarbon group or a heteroatom-containing C1-C27 polyvalent hydrocarbon group; each R 5 independently represents a C1-C28 polyvalent hydrocarbon group; R 6 represents a C1-C20 monovalent hydrocarbon group; and a, b, c, d, e, f, m, n, o, p, and x are independent from one another, each of a, c, and e represents a number of 1 to 3, each of b and d represents a number of 1 to 5, f represents a number of 0 to 5, each of m and p represents a number of 1 to 100, n represents a number of 1 to 15, o represents a number of 0 to 10, and x represents a number of 1 to 10. wherein each G 1 independently represents a C1-C30 polyvalent hydrocarbon group containing a polysulfide group, represented by [(CH 2) b -] c R 4 [-(CH 2) d S x -] e; each G 2 independently represents a C1-C30 polyvalent hydrocarbon group containing a polysulfide group, represented by [(CH 2) b -] c R 5 [-(CH 2) d S x -] e; each of Y 1 and Y 2 independently represents a silyl group represented by -SiX 1 X 2 X 3, a hydrogen atom, a carboxyl group, or an ester group represented by -C(=O)OR 6; each X 1 independently represents -Cl, -Br, -OH, -OR 6, or R 6 C (=O)O-; each of X 2 and X 3 independently represents a hydrogen atom, R 6, X 1, or a -OSi-containing group formed by silanol condensation; each of R 1 and R 3 independently represents a C1-C20 divalent hydrocarbon group; each R 2 independently represents a linear hydrocarbon group represented by -(CH 2) f -; each R 4 independently represents a C1-C28 polyvalent hydrocarbon group or a heteroatom-containing C1-C27 polyvalent hydrocarbon group; each R 5 independently represents a C1-C28 polyvalent hydrocarbon group; R 6 represents a C1-C20 monovalent hydrocarbon group; and a, b, c, d, e, f, m, n, o, p, and x are independent from one another, each of a, c, and e represents a number of 1 to 3, each of b and d represents a number of 1 to 5, f represents a number of 0 to 5, each of m and p represents a number of 1 to 100, n represents a number of 1 to 15, o represents a number of 0 to 10, and x represents a number of 1 to 10.