A method of peeling a mother protective film from a mother display panel includes: laminating the mother protective film on the mother display panel, the mother display panel comprising a plurality of display cells each including a display area and a peripheral area in an outer portion of the display cells; forming a target area and a dummy area on the mother protective film by forming a cutting line having a closed loop shape enclosing the target area corresponding to the display cells and an additional cutting line in a first direction near the cutting line; arranging a fixing member on the mother protective film within the target area enclosed by the cutting line; and physically peeling off the dummy area from the mother display panel.