A width-adjustable packaging bag shaper, a bag maker, a packaging machine, and a method. The packaging machine including the bag maker, a traction device and a heat sealing device are respectively arranged above the bag maker, and a width adjustment device adjusts the distances between different sub bottom plates in a front bottom plate and a rear bottom plate by using a leadscrew and slide block mechanism, and then adjusts the width of a bottom plate. The leadscrew and slide block mechanism is used as the width adjustment device of the automatic width-adjustable noodle packaging bag shaper system, and four bottom plates are respectively fixed to the width adjustment device, so the leadscrew and slide block mechanism in operation is accurate in range of adjustment, is suitable for various widths of packaging bags, and has very important significance for the three-dimensional shaping effect of the packaging bags.