An aspect of the present invention relates to a method of manufacturing a polarizing plastic lens, which comprises an upper mold positioning step of positioning an upper mold so that a nonmolding surface faces up and a molding surface faces down, an adhesive column forming step of discharging a thixotropic curable adhesive from a discharge nozzle positioned beneath the molding surface of the upper mold to form adhesive columns on a rim portion of the molding surface of the upper mold, a bonding step of bonding the upper mold and a polarizing film by means of the adhesive columns that have been formed, an adhesive column curing step of subjecting the adhesive columns to a curing treatment after the bonding step, a casting mold assembling step of assembling a casting mold having a cavity within which the polarizing film has been positioned with the upper mold to which the polarizing film has been bonded, a lower mold positioned opposite the upper mold so as to sandwich the polarizing film, and a sealing member maintaining a spacing between the upper mold and lower mold, and a polymerizing and curing step of casting a curable composition into the cavity, and polymerizing and curing the curable composition that has been cast to provide a polarizing plastic lens within which the polarizing film is positioned.