Abstract: A multiple-line automatic packing machine configured to produce packed products each having three sealed sides simultaneously and continuously in multiple lines. A vertical sealing device includes a vertical sealing belt. Vertical sealing is performed by rotating the vertical sealing belt along a conveying direction of the packing film at the same speed as conveying speed of the packing film while pressing the vertical sealing belt against a former through intermediation of an overlapping portion of the packing film. Further, a lateral sealing device performs lateral sealing on a portion of the packing film corresponding to a lower portion of a packing bag, and then performs lateral sealing on a portion of the packing film corresponding to an upper portion of the packing bag while moving upward and downward in synchronization with the packing film continuously conveyed at a predetermined speed.