A rubber composition for a tire, comprises: a rubber component; and a hydrated silica having particles each provided with micropores with openings in the range of 1.2 × 10 5 nm to 6 nm formed at outer surface of the particle, wherein the rubber component contains a modified polymer reactive to the hydrated silica, in measurement according to a mercury press-in method using a mercury porosimeter of the hydrated silica, provided that: "M1" (nm) represents diameter of the opening exhibiting the maximum value of mercury charge rate when pressure is increased from 0.0069 MPa to 220 MPa (1 PSI to 32000 PSI); "M2" (nm) represents diameter of the opening exhibiting the maximum value of mercury discharge rate when pressure is decreased from 220 MPa to 0.0069 MPa (32000 PSI to 1 PSI); "IB" represents "ink bottle-shaped micropore index"; IB = M2 − M1 "CTAB" (m 2 /g) represents specific surface area by cetyltrimethylammonium bromide adsorption; "weight loss on ignition" (mass %) represents weight loss when the hydrate silicate is heated at 750 °C for 3 hours; and "weight loss on heating" (mass %) represents weight loss when the hydrate silicate is heated at 105 °C for 2 hours, IB and CTAB satisfy following formula and formula and "weight loss on ignition" and "weight loss on heating" satisfy formula IB ≤ − 0.56 × CTAB + 110.4 when CTAB ≤ 140 IB ≤ − 0.20 × CTAB + 60.0 when CTAB > 140 ("weight loss on ignition" - "weight loss on heating") ≥ 2.5 (mass %) ···, and the value of said "CTAB" is measured in accordance with ASTM D3765-92 but with the following modifications: preparing cetyltrimethylammonium bromide ("CE-TRAB") standard solution in the place of "IRB#3" (83.0 m 2 /g) as the standard solution according to ASTM D3765-92; carrying out standardization of hydrated silica OT (sodium di-2-ethylhexyl sulfosuccinate) solution by using the CE-TRAB standard solution; assuming that cross sectional area per one CE-TRAB molecule adsorbed on the hydrated silica surface is 0.35 nm 2; and regarding a specific surface area (m 2 /g) calculated from an amount of CE-TRAB adsorption based on the aforementioned assumption as a value of CTAB. a rubber component; and a hydrated silica having particles each provided with micropores with openings in the range of 1.2 × 10 5 nm to 6 nm formed at outer surface of the particle, wherein the rubber component contains a modified polymer reactive to the hydrated silica, in measurement according to a mercury press-in method using a mercury porosimeter of the hydrated silica, provided that: "M1" (nm) represents diameter of the opening exhibiting the maximum value of mercury charge rate when pressure is increased from 0.0069 MPa to 220 MPa (1 PSI to 32000 PSI); "M2" (nm) represents diameter of the opening exhibiting the maximum value of mercury discharge rate when pressure is decreased from 220 MPa to 0.0069 MPa (32000 PSI to 1 PSI); "IB" represents "ink bottle-shaped micropore index"; IB = M2 − M1 "CTAB" (m 2 /g) represents specific surface area by cetyltrimethylammonium bromide adsorption; "weight loss on ignition" (mass %) represents weight loss when the hydrate silicate is heated at 750 °C for 3 hours; and "weight loss on heating" (mass %) represents weight loss when the hydrate silicate is heated at 105 °C for 2 hours, "M1" (nm) represents diameter of the opening exhibiting the maximum value of mercury charge rate when pressure is increased from 0.0069 MPa to 220 MPa (1 PSI to 32000 PSI); "M2" (nm) represents diameter of the opening exhibiting the maximum value of mercury discharge rate when pressure is decreased from 220 MPa to 0.0069 MPa (32000 PSI to 1 PSI); "IB" represents "ink bottle-shaped micropore index"; IB = M2 − M1 "CTAB" (m 2 /g) represents specific surface area by cetyltrimethylammonium bromide adsorption; "weight loss on ignition" (mass %) represents weight loss when the hydrate silicate is heated at 750 °C for 3 hours; and "weight loss on heating" (mass %) represents weight loss when the hydrate silicate is heated at 105 °C for 2 hours, IB and CTAB satisfy following formula and formula and "weight loss on ignition" and "weight loss on heating" satisfy formula IB ≤ − 0.56 × CTAB + 110.4 when CTAB ≤ 140 IB ≤ − 0.20 × CTAB + 60.0 when CTAB > 140 ("weight loss on ignition" - "weight loss on heating") ≥ 2.5 (mass %) ···, and the value of said "CTAB" is measured in accordance with ASTM D3765-92 but with the following modifications: preparing cetyltrimethylammonium bromide ("CE-TRAB") standard solution in the place of "IRB#3" (83.0 m 2 /g) as the standard solution according to ASTM D3765-92; carrying out standardization of hydrated silica OT (sodium di-2-ethylhexyl sulfosuccinate) solution by using the CE-TRAB standard solution; assuming that cross sectional area per one CE-TRAB molecule adsorbed on the hydrated silica surface is 0.35 nm 2; and regarding a specific surface area (m 2 /g) calculated from an amount of CE-TRAB adsorption based on the aforementioned assumption as a value of CTAB.