The present invention provides a rubber composition that can enhance the fuel economy, wet-grip performance, and abrasion resistance in a balanced manner, and a pneumatic tire using this rubber composition. The present invention relates to a rubber composition that contains a rubber component, silica, and a silane coupling agent, wherein the rubber component contains, based on 100% by mass of the rubber component, not less than 5% by mass of a conjugated diene polymer containing a constituent unit based on a conjugated diene and a constituent unit represented by formula (I) below, at least one terminal of the polymer being modified with a specific compound; an amount of the silica is 5 to 150 parts by mass per 100 parts by mass of the rubber component; and the silane coupling agent contains a mercapto group.