A kneading experiment of thermoplastic resin and carbon black (material for toner) was carried out with a continuous kneader under various feeding rates.In addition to the measurements of the mixing torque in kneading and the residence time of the material, an assessment of a dispersion state of carbon black was attempted by means of image analysis and the validity of this method was examined.From the results, it is suggested that the degree of dispersion can be determined by the density of aggregation of the kneaded material, and also it is clarified that the degree of dispersion in the kneaded material increases with a prolongation of the residence time, that is, as the mixing action works both radially and axially, or with an increase of the kneading energy.