A rubber composition of a tire, comprising: a rubber component; a silica; and a silane coupling agent; the rubber component containing a specific conjugated diene rubber and a natural rubber, in the rubber component, the content of the specific conjugated diene rubber being 35 mass% or more and the content of the natural rubber being 10 mass% or more, the specific conjugated diene rubber being a conjugated diene rubber comprising a polymer block containing an isoprene monomer unit and a polymer block containing a 1,3-butadiene monomer unit and having a modified structure by a siloxane compound at least at one terminal, in the conjugated diene rubber: at least one of the polymer block and the polymer block containing a unit of a vinyl compound containing an amino group as a functional group interactable with a silica; the polymer block having a weight average molecular weight (Mw) in a range of from 1000 to 30000, and an entire weight average molecular weight (Mw) in a range of from 50000 to 5000000; an entire aromatic vinyl monomer unit content being from 30 to 45 mass%; and an entire vinyl bond content being from 15 to 35 mass%, the content of the silica being from 50 to 150 parts by mass per 100 parts by mass of the rubber component, and the content of the silane coupling agent being from 3 to 30 mass% with respect to the content of the silica. a rubber component; a silica; and a silane coupling agent; the rubber component containing a specific conjugated diene rubber and a natural rubber, in the rubber component, the content of the specific conjugated diene rubber being 35 mass% or more and the content of the natural rubber being 10 mass% or more, the specific conjugated diene rubber being a conjugated diene rubber comprising a polymer block containing an isoprene monomer unit and a polymer block containing a 1,3-butadiene monomer unit and having a modified structure by a siloxane compound at least at one terminal, in the conjugated diene rubber: at least one of the polymer block and the polymer block containing a unit of a vinyl compound containing an amino group as a functional group interactable with a silica; the polymer block having a weight average molecular weight (Mw) in a range of from 1000 to 30000, and an entire weight average molecular weight (Mw) in a range of from 50000 to 5000000; an entire aromatic vinyl monomer unit content being from 30 to 45 mass%; and an entire vinyl bond content being from 15 to 35 mass%, the content of the silica being from 50 to 150 parts by mass per 100 parts by mass of the rubber component, and the content of the silane coupling agent being from 3 to 30 mass% with respect to the content of the silica. at least one of the polymer block and the polymer block containing a unit of a vinyl compound containing an amino group as a functional group interactable with a silica; the polymer block having a weight average molecular weight (Mw) in a range of from 1000 to 30000, and an entire weight average molecular weight (Mw) in a range of from 50000 to 5000000; an entire aromatic vinyl monomer unit content being from 30 to 45 mass%; and an entire vinyl bond content being from 15 to 35 mass%, the content of the silica being from 50 to 150 parts by mass per 100 parts by mass of the rubber component, and the content of the silane coupling agent being from 3 to 30 mass% with respect to the content of the silica.