PURPOSE: To obtain the titled rubber composition excellent in tensile strength, resiliency, heat build-up, etc., by adding carbon black, sulfur, a vulcanization accelerator, etc., to a stock rubber containing a specified living polymer having C=S bonds in the molecule.

CONSTITUTION: Styrene is copolymerized with butadiene in a hydrocarbon solvent in the presence of an organolithium catalyst (e.g., ethyllithium) to prepare a living polymer having a vinyl bond content in the butadiene part of 10W70% and a MW distribution (Mw/Mn) of 1.2W3. This living polymer is reacted with carbon disulfide, a xanthogen compound, a dithio acid compound (e.g., methyl dithioacetate) or the like to introduce C=S bonds into the molecule. 10W100pts. wt. carbon black, 0.3W5pts.wt. sulfur and a vulcanization accelerator are added to 100pts.wt. stock rubber containing at least 10wt% above obtained polymer of a Mooney viscosity of 20W150.