Twin screw extruders are widely used as a continuous manufactureing machine of polymeric materials such as polymer alloys, blends, composites and other materials. Our research group has been studied on the development of computer simulation technique to predict the materials behavior in a twin-screw extruder and the evaluation method of mixing performance based on the simulation results. The simulation has applied to evaluate the mixing by pitched-tip kneading discs whose tips are pitched to the screw axis. We have studied the performance of mixing elements with different combinations of stagger and tip directions for pitched-tip kneading discs. In this study, we carry out the twin-screw extrusion expariment for a blend of ABS (acrylonitrile-butadiene-styrene copolymer) and AS (acrylonitrile-styrene copolymer). We performed the morphology observation via scanning electron microscope and evaluated the diameter distribution of despersed rubber particles. We also measured the rheological properties. We compared these results with the mixing performance obtained by the previous simulation, and discussed the melt mixing mechanism by pitched-tip kneading discs and reliability of the numerical simulation. Keywords: Twin Screw Extruder, Polymer Blend, Numerical Simulation, Rheological Property, Morphology