A film opening mechanism in which, regardless of whether a tubular film is long or short, a deviation in timing of delivery of the tubular film from a mandrel does not occur, and the tubular film does not become wrinkled. The film opening mechanism includes a mandrel for causing the tubular film to be opened into a predetermined state by fitting it thereon; a film transport unit composed of an upstream-side feed belt unit and a downstream-side feed belt unit, each having a feed belt which nips the tubular film fitted on the mandrel in cooperation with the mandrel to transport the tubular film toward a lower side of the mandrel; and attraction means for attracting the mandrel and the feed belt to each other by means of a magnetic attractive force.