A process for preparing a vulcanized rubber composition comprising: (a) a step of preparing a master batch comprising a butadiene rubber and not less than 40 parts by mass of silica based on 100 parts by mass of the butadiene rubber, (b) a step of preparing a master batch comprising an isoprene rubber and not less than 15 parts by mass of silica based on 100 parts by mass of the isoprene rubber, (c) a step of kneading the master batch obtained in the step (a) and the master batch obtained in the step (b), and (d) a step of vulcanizing a kneaded product obtained in the step (c), wherein the vulcanized rubber composition comprises: a phase comprising the butadiene rubber and silica (BR phase), and a phase comprising the isoprene rubber and silica (IR phase), wherein the BR phase and the IR phase are incompatible with each other, wherein the term "incompatible" means that an averaged equivalent circle radius of a discontinuous phase in the section of the vulcanized rubber composition is 100 nm or more when evaluated based on an image taken with a scanning electron microscope, an abundance ratio α of silica in the BR phase 100 to 500 hours after completion of a vulcanization step satisfies the following Relation 1, and a proportion β of the butadiene rubber satisfies the following Relation 2: 0.3 ≤ α ≤ 0.7 0.4 ≤ β ≤ 0.8 wherein α = Amount of silica in BR phase / (Amount of silica in BR phase + Amount of silica in IR phase) and β = Mass of butadiene rubber in vulcanized rubber composition/ (Mass of butadiene rubber in vulcanized rubber composition + Mass of isoprene rubber in vulcanized rubber composition), and wherein the vulcanized rubber composition comprises a filler comprising 1 to 95 parts by mass of carbon black having a nitrogen adsorption specific surface area (N 2 SA) of 90 to 300 m 2 /g and 25 to 80 parts by mass of silica based on 100 parts by mass of the total rubber components, wherein the N 2 SA is measured according to JIS K 6217-2. (a) a step of preparing a master batch comprising a butadiene rubber and not less than 40 parts by mass of silica based on 100 parts by mass of the butadiene rubber, (b) a step of preparing a master batch comprising an isoprene rubber and not less than 15 parts by mass of silica based on 100 parts by mass of the isoprene rubber, (c) a step of kneading the master batch obtained in the step (a) and the master batch obtained in the step (b), and (d) a step of vulcanizing a kneaded product obtained in the step (c), wherein the vulcanized rubber composition comprises: a phase comprising the butadiene rubber and silica (BR phase), and a phase comprising the isoprene rubber and silica (IR phase), wherein the BR phase and the IR phase are incompatible with each other, wherein the term "incompatible" means that an averaged equivalent circle radius of a discontinuous phase in the section of the vulcanized rubber composition is 100 nm or more when evaluated based on an image taken with a scanning electron microscope, an abundance ratio α of silica in the BR phase 100 to 500 hours after completion of a vulcanization step satisfies the following Relation 1, and a proportion β of the butadiene rubber satisfies the following Relation 2: 0.3 ≤ α ≤ 0.7 0.4 ≤ β ≤ 0.8 wherein α = Amount of silica in BR phase / (Amount of silica in BR phase + Amount of silica in IR phase) and β = Mass of butadiene rubber in vulcanized rubber composition/ (Mass of butadiene rubber in vulcanized rubber composition + Mass of isoprene rubber in vulcanized rubber composition), and wherein the vulcanized rubber composition comprises a filler comprising 1 to 95 parts by mass of carbon black having a nitrogen adsorption specific surface area (N 2 SA) of 90 to 300 m 2 /g and 25 to 80 parts by mass of silica based on 100 parts by mass of the total rubber components, wherein the N 2 SA is measured according to JIS K 6217-2. a phase comprising the butadiene rubber and silica (BR phase), and a phase comprising the isoprene rubber and silica (IR phase), wherein the BR phase and the IR phase are incompatible with each other, wherein the term "incompatible" means that an averaged equivalent circle radius of a discontinuous phase in the section of the vulcanized rubber composition is 100 nm or more when evaluated based on an image taken with a scanning electron microscope, an abundance ratio α of silica in the BR phase 100 to 500 hours after completion of a vulcanization step satisfies the following Relation 1, and a proportion β of the butadiene rubber satisfies the following Relation 2: 0.3 ≤ α ≤ 0.7 0.4 ≤ β ≤ 0.8 wherein α = Amount of silica in BR phase / (Amount of silica in BR phase + Amount of silica in IR phase) and β = Mass of butadiene rubber in vulcanized rubber composition/ (Mass of butadiene rubber in vulcanized rubber composition + Mass of isoprene rubber in vulcanized rubber composition), and wherein the vulcanized rubber composition comprises a filler comprising 1 to 95 parts by mass of carbon black having a nitrogen adsorption specific surface area (N 2 SA) of 90 to 300 m 2 /g and 25 to 80 parts by mass of silica based on 100 parts by mass of the total rubber components, wherein the N 2 SA is measured according to JIS K 6217-2.