MODIFIED CONJUGATED DIENE RUBBER, METHOD FOR PRODUCING SAME, AND RUBBER COMPOSITION

[Problem] To provide a method for producing conjugated diene rubber usable as a starting material of cross-linked rubber which is used for a tire tread or the like and allows enhancement of low fuel consumption propoerty. [Means for Resolution] A method of producing modified conjugated diene rubber through a process including (a) a step of producing a modified conjugated diene polymer through reaction of a conjugated diene polymer having an alkali metal or alkaine-earth metal active terminal wherein the conjugated diene polymer is a polymer produced through polymerization of a conjugated diene compound with an aromatic vinyl compound with a first alkoxysilane compound which has both an alkoxysilyl group with two or more alkoxy groups and at least one group convertible into an onium by means of an agent for producing onium per molecule, and (b) a step of mixing the modified conjugated diene polymer, an agent for producing onium, a second alkoxysilane compound having an alkoxysilyl group and at least one group convertible into an onium by means of the agent for producing onium per molecule and a condensation catalyst containing metal element(s) for alkoxysilane compounds.