To obtain carbon black treated so as to link a specific silicon compound to the surface of the carbon black by chemical bond, to provide a method for producing the carbon black, to obtain both a rubber composition having improved hysteresis loss and a tire having extremely improved grip performances by using the modified carbon black.

This rubber composition is obtained by compounding 100 pts.wt. of a rubber component composed of a natural rubber and/or a synthetic diene- based rubber with 30-200 pts.wt. of modified carbon black having a Si-O-C bond or Si-C bond (a carbon directly bonded to Si is an aromatic carbon) on the surface. This pneumatic tire is obtained by using the rubber composition especially in thread. The modified carbon black is obtained by bringing carbon black into contact with a silicon compound of the general formula (R1O)mSiR24-m [R1 is a 1-3C alkyl group or a phenyl group; m is an integer of 2-4] or the like in a vapor phase.