A method used for manufacturing a polarizing film is provided. The method includes enabling a polarizing film precursor to pass through a plurality of treatment grooves in sequence so as to form a polarizing film. The method further includes performing a total organic carbon volume monitoring procedure when the polarizing film precursor passes through at least one among the treatment grooves and a groove liquid adjustment procedure of reducing the total organic carbon volume of groove liquid in the treatment groove to a value lower than or equal to a monitoring value when the total organic carbon volume of the groove liquid in the treatmtne groove surpasses a monitoring value of the treatment groove, wherein the monitoring value is smaller than or equal to 800 ppm. The method provided by the invention includes the montoring procedure so as to improve the quality of the polarizing film and a polarizing panel made of the polarizing film.