PURPOSE: To provide a reinforcing carbon black which can impart high hardness, tensile strength, etc. to elastomer while keeping excellent resilience when blended with an elastomer component, consisting of a soft black having specified physical properties.

CONSTITUTION: Reinforcing carbon black consists of a soft black having a particle size range giving a specific surface area of 35W65m2/g as measured by BET method and has selected characteristics such that a DBP oil absorption is 150ml/100g or above and a Dst mode diameter (mμ) is a value as defined by the formula [0.6(DBP)-3.96(N2SA)+300] or below.The carbon black belongs to soft black having a relatively large particle size as carbon black to be blended with the elastomer component of rubber or plastic. However, when the structure is high and the Dst mode diameter is within the range as specified above, the carbon black can impart both high resilience and a relatively high reinforcing performance to the elastomer.