The embodiment of the invention provides a film blowing machine, and relates to the technical field of plastic manufacturing. The film blowing machine comprises an extruder, a mould head, a fixed core rod, a wind ring, a traction roller and an inverted-V-shaped rack, wherein a joint of the mould head and the fixed core rod is provided with a first air outlet; the first air outlet is arranged at the inner side of a discharge hole of the mould head; the fixed core rod is provided with a second air outlet; and the second air outlet is arranged on the rod body of the fixed core rod. According to the film blowing machine provided by the embodiment, the rod body of the fixed core rod is provided with the second air outlet, so that air-out is carried out through the second air outlet when the film blowing machine needs carrying out film blowing in a relatively large blow-up ratio, and therefore, uneven film thickness caused by too strong wind provided by the first air outlet at the joint of the mould head and the fixed core rod is avoided; and meanwhile, the first air outlet is mutually matched with the second air outlet, sot that the blow-up ratio of the film blowing machine can be regulated more flexibly.