The invention relates to a method of manufacturing a polarizing lens, including conducting curved surface processing to change a shape of a polarizing film into a shape of a curved surface, conducting heat treatment by heating polarizing film that has been processed into a curved surface to a heating temperature of equal to or higher than 105° C. but less than 150° C., assembling an upper mold, a lower mold, and a seal member to provide a casting mold having a cavity within which the polarizing film following heating treatment is positioned, upper and lower molds being positioned opposite each other to sandwich the polarizing film at a space therebetween, and seal member sealing space between the upper and lower molds, casting a curable composition into the cavity, curing curable composition to provide a polarizing lens within which a polarizing film is positioned, and separating polarizing lens thus provided from casting mold.