To provide a diene based rubber composition which, one suitably usable as a vulcanization molding material for a base tread, a belt cushion, an upper part soft bead filler and the like of a pneumatic tire, can give a vulcanization molding product having low heat build-up, a high elongation at break and excellent heat-aging resistance without inviting an increase of the viscosity and a drop of the elastic modulus.

The diene based rubber composition incorporates, based on 100 pts.wt. of a diene based rubber, 4-9 pts.wt. of zinc monomethacrylate and 4-10 pts.wt. of a cyclic polysulfide compound represented by general formula (I) (wherein R is a substituted or unsubstituted 2-10C alkylene group, or an alkylene group including a substituted or unsubstituted 2C-18C oxyalkylene group; x is an integer of 2-6; and n is an integer of 1-15).