Manufacturing method of polarizer sufficiently increases the single transmittance even if the humidification time is shortened when the polarizer is subjected to a humidification step

The purpose of the invention is to provide a manufacturing method capable of producing polarizer that can sufficiently increase the single transmittance even if the humidification time is shortened when the polarizer is subjected to a humidification step. The solution is the method of manufacturing polarizer according to the embodiment of the invention, which includes: a first dyeing step of dyeing a polyvinyl alcohol resin film with a dichroic substance; a stretching step of stretching the polyvinyl alcohol resin film experienced with the first dyeing step in a boric acid aqueous solution; and a second dyeing step of dissolving the boric acid from the polyvinyl alcohol resin film experienced with the stretching step, and using the dichroic substance to dye the polyvinyl alcohol resin film.