the present invention proposes a plastic film guiding device of a packaging machine , which comprises a frame , a screw rod , a walking block , a positioning rod , a pair of slanting rods , and a pair of slide bodies . the plastic film guiding device of the present invention is arranged in suspended way to reduce its contact with the surface of a machine table so that the present invention suffers less heat to facilitate the adjustment . most importantly , the present invention has instant width - adjusting function , and can simultaneously perform identical adjustments to the widths of both sides . the adjustment is fast , and the positions of movement are exact . moreover , fine adjustment of width can be performed at any time during the operation of the machine .