The present invention provides a belt-like plastic film conveyance method capable of accurately folding a belt-like plastic film at an intended position in a width direction by appropriately changing a conveyance path of the belt-like plastic film being continuously conveyed from the upstream side to the downstream side from a film roll or the like, a belt-like plastic film conveyance guide, and a bag-making device. When conveying the belt-like plastic film being conveyed from the upstream side toward the downstream side while wrapping the plastic film at least at a widthwise center region thereof around an outer surface of a guiding body, the conveyance path of the belt-like plastic film is changed by sliding the belt-like plastic film along the outer surface of the guiding body by changing frictional resistance and tension of the belt-like plastic film to the guiding body by moving, rotating, or tilting the guiding body, around...
