A melt-kneading method for filling material-containing resin or elastomer includes: a step of preparing a filling material as a filler and a resin or elastomer comprising an incompatible blend; and a step of introducing the filling material-containing resin or elastomer into a material feed part provided at an end of a cylindrical melt-kneading part having a heater and provided with a screw, and then melt-kneading the filling material-containing resin or elastomer under conditions where the rotation speed of the screw is about 600 rpm to about 3,000 rpm and its shear rate is about 900 to about 4,500 sec−1, thereby forming a co-continuous structure comprising the incompatible blend.