To provide a rubber composition suppressed in increase in rubber hardness with the lapse of time.

The rubber composition comprises 100 pts.wt. of a raw material rubber mainly composed of one or more rubbers selected from the group consisting of a styrene-butadiene copolymer rubber, a natural rubber, a polyisoprene rubber and other diene rubbers and, incorporated therewith, 3-80 pts.wt. of a petroleum-based process oil having an aroma content of 20-40 wt.% and a pour point of at least 35°C.