A method of peeling off the protective film includes: providing a panel lower sheet, where a protective film is provided on one surface of the plane lower sheet and the protective film has a bending line extending in a first direction parallel to opposing sides thereof; gripping a portion of the protective film; moving the gripped portion of the protective film in a second direction which is a thickness direction thereof; and moving the panel lower sheet in a third direction perpendicular to the bending line.