We observed a relationship between the size of one polystyrene (PS) molecule in a dilute solution and in an extractive or evaporative solid state prepared from a PS dilute solution. In the both cases we observed the scaling relationship between the molecular weight and the molecular size. And the distributions of these sizes were also almost same. Though the scaling exponent was about 0.6 in the dilute solution, the exponent of the mono-molecule solid PS was 0.6 below M_w=7.5×10⁶ and 0.33 above M_w=7.5×10⁶. This was consistent with the experimental result that the ELSD (evaporative light scattering detector) peak area of a PS solution became lower above a critical molecular weight even if the PS mass concentration was same. Above a critical molecular weight the PS mono-molecular solid particle would shrink smaller than the value which was speculated form the size in the dilute solution.