To provide a polyvinyl alcohol based polymer film useful as the raw material for producing polarizing films having a reduced number of defects, and a polarizing film prepared by using the same.

The polyvinyl alcohol based polymer film has a dissolved amount of the polyvinyl alcohol based polymer, when 100 cm2 polyvinyl alcohol based polymer is left to stand in 1 liter water of 50°C for 4 hours, of 1-100 ppm. The polarizing film is prepared by using this film.