In these days, the amount of plastic waste is being extremely large, and thus it is very important to establish effective process of recycling them as soon as possible. However, the mechanical properties of the products made from waste plastics are inferior to those of products molded from virgin plastics. Recently found that the main cause of this inferior property was reproducible physical degradation. And also we found that by selecting the compression molding condition, we can improve the mechanical properties of recycled plastic as virgin plastic. On the other hand, in order to disseminate material recycling more generally, it is important to show this principle can be applied to a wide variety of molding methods clearly. Especially, if we can produce highly applicable pellets as well as virgin, its utility value is very high. Therefore, in this time, we used waste container and packaging recycled plastic, and prepared many kinds of pellets under various conditions. We also evaluated mechanical properties of the injection molded products of these pellets. As a result, we found that the mechanical properties of the injection molded article are largely dependent on the pelletizing condition. Moreover, we found that physical properties of injection molded articles are greatly improved by pelletizing without applying too much shear at a relatively high temperature for a long time.From the consideration, we added a new equipment element to the pelletizer machine, and found it works so well. This finding will greatly contribute to the progress of material recycling in the future.