A method of mixing a rubber composition includes a carbon introduction step and a uniform dispersion step. In the carbon introduction step, on the basis of a deviation between a rate of temperature increase of the rubber mixture (R) and a target value, at least one of a ram pressure (Pr) and a rotational speed (N) of the mixing rotor (2) is PID controlled so that the ultimate temperature of the rubber mixture (R) at the conclusion of the step is within a tolerance range. In the uniform dispersion step, the ram pressure (Pr) or the rotational speed (N) of the mixing rotor (2) is adjusted to reduce a deviation between a value based on successively detected data associated with a predetermined control target and a target value.