Rubber composition fabrication method and rubber composition

A method for producing a rubber composition containing a rubber wet master batch, comprising:

• a masticating process of plasticizing/dispersing only the rubber wet master batch, and a kneading process of adding one or more blending agents other than any vulcanization-related blending agent to the rubber wet master batch yielded after the masticating process, wherein the masticating and kneading processes are performed by use of the same mixing/dispersing device, and
• the masticating process comprises:
• step 1 of charging the rubber wet master batch into an enclosed kneading chamber that has a stirring rotor showing a rotation speed controllable automatically through a control unit and that is capable of detecting and outputting an internal temperature, step 2 of setting a first control time and a first target temperature in the control unit, and
• step 3 of stirring the rubber wet master batch inside the kneading chamber while making a PID control for adjusting a first actually measured temperature in the kneading chamber to the first target temperature through the control unit on the basis of information on the first actually measured temperature and the first target temperature, thereby automatically controlling the rotation speed, until the first control time elapses after the completion of the steps 1 and 2,
• wherein the first actually measured temperature in the kneading chamber is an internal temperature of the kneading chamber detected by a temperature sensor and sent to the control unit during the masticating process, and the first target temperature in the masticating process is 160° C. or more and 180° C. or lower, and the first control time is 0.5 to 10 minutes.