To provide a filtration method for a polymer solution, capable of prolonging service life of filtration and making filtration accuracy high precision, and to provide a method for film production from the filtered solution, capable of increasing film quality by applying the filtration method.

The filtration method for the polymer solution for removing foreign substances in the polymer solution by dissolving a polymer in a solvent comprises three steps using filter devices 30A to 30C, and, at the end thereof, uses a guard filter device 30D for removing foreign substances from outside other than foreign substances in a dope stock solution 41 so that the four step filtration in total is performed.