There is provided a method of preparing biodegradable dual pore polymer scaffolds, comprising the steps of: maintaining a polymer solution containing a biodegradable polymer, an effervescent mixture of carbonate and organic acid, and solvent at a temperature range of −196° C. to ambient temperature so as to evaporate the solvent and produce a polymer sample; and foaming the polymer sample in a mixed solution of water and alcohol. According to the present invention, the pore size of the polymer scaffolds can be easily controlled, and biodegradable polymer scaffolds can be more simply prepared compared to conventional methods such as salt leaching technique, phase separation technique or gas foaming technique. Further, since the biodegradable polymer scaffolds prepared according to the present invention have a high surface area and porosity without formation of skin layer, secretion of toxic substances and remnant phenomenon, they can be advantageously used for regenerating almost all living tissues and organs in tissue engineering.