Embodiments of the present invention may provide a method of preparing biodegradable polyester polymer materials both in a filament type and a sheet type using a compressed gas. The method of the present invention comprises the following steps: 1) preparing biodegradable polyester polymers through a solution-state polymerization process of a cyclic monomer using a compressed gas as a reaction solvent in the presence of a catalyst; 2) performing a flash-spinning process of the biodegradable polyester polymers prepared above to form a polymer material in a filament type; and 3) performing a calendering process of the polymer material in a filament type prepared above to form a polymer material in a point-bonded sheet type. Since the method according to the embodiments of the present invention has several advantages in that it employs compressed gas as a reaction solvent, which does not require the addition of a stabilizer and the solution-state polymerization, flash-spinning and callendering processes are conducted in a single consecutive process. This can be effectively used in the manufacture of biodegradable polyester polymer materials, which can be used as a biodegradable and biocompatible material useful in the fields of medicine, chemistry, agriculture, environment and the like.