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The cooling and crystallization process of crystalline polymers from the melt state greatly influence their inner structures and mechanical properties. The annealing process between the glass transition temperature and melting temperature also strongly influences their mechanical properties. For an amorphous polymer, it is well known that annealing under the glass transition temperature introduces changes in physical properties due to entropy relaxation. For casting solutions of amorphous polymers under the glass transition temperature, the molding and solidification history is reflected in their viscoelastic properties (especially tand). On the other hand, when molecular orientation occurs during the molding process, with the use of a polarizing microscope we can see that such orientation disappears when the sample is held for longer than the longest relaxation time above the melting point in the case of a crystalline polymer and above the glass transition temperature in the case of an amorphous polymer. This means that the conformation of the polymer becomes random when it retained in a fluid state for longer than the longest relaxation time because the center of gravity of the molecules can move. However, Andrianova previously showed that the melt viscoelastic properties of amorphous polystyrene strongly depended on the history of dissolution. He also raised the possibility that an amorphous polymer develops a specific structure even in the molten state. In our previous paper, we measured the mechanical properties of compressed thin films made from recycled polystyrenes and found that they strongly depend on the molding history. This suggests that the orientation of polymer molecules caused by the molding history does not relax easily. In addition, we found that the mechanical properties had been changing under hot compression that lasted 100 times longer than the longest relaxation time. We also found that the polymer showed greater ductility with an increase in the duration of compression. These results seem to suggest that relaxation of the orientation history by molding requires a longer time than the longest relaxation time based on viscoelastic measurements. However, they also suggest that this phenomenon is not due to a simple relaxation mechanism because the stress-strain curve has a profile that is completely different from that of the virgin material. In this study, we evaluated the dependence of the Development of an Internal Structure by Amorphous Polymer in the Melt State