PROBLEM TO BE SOLVED: To provide a method for manufacturing a polymer nano fine-porous membrane which does not bring about remarkable lowering of flux even through a drying step.SOLUTION: A method for manufacturing a polymer nano fine-porous membrane is the method for manufacturing the polymer nano fine-porous membrane prepared from a polymer solution. The method includes the steps of: forming the polymer nano fine-porous membrane by using the polymer solution in which a polymer is dissolved; heating a high boiling point solution of which boiling point is a crystallization temperature of the polymer or more to a temperature of the crystallization temperature of the polymer or more and less than a melting point; heating the formed polymer nano fine-porous membrane, in the heated high boiling point solution, to the crystallization temperature or more; washing the polymer nano fine-porous membrane after heating; and drying the polymer nano fine-porous membrane after washing. As the result, the remarkable lowerin
