PURPOSE: To prevent a lead string, which is attached to a packaging material when a bag body is formed with the packaging material, from tangling or being cut at the time of sealing.

CONSTITUTION: A packaging material 18 is sealed by a longitudinal sealing machine 60 to form a bag body while feeding the packaging material 18 in the longitudinal direction. A lead string 13 is fixed to the packaging material 18 in a loop shape, when the bag body is formed. A guide member 70 on which the lead string 13 is placed across when the lead string 13 is fixed is provided. Accompanying with the feeding of the packaging material 18, the lead string 13 runs along the guide member 70, and is prevented from entering the packaging material 18 side. A suction member 75 is provided at a location which is close to the lower end of the guide member 70 to keep the lead string 13 under a condition in which the lead string 13 stays away from the longitudinal sealing machine 60 and a lateral sealing machine, and the lead string 13 is prevented from being cut by the sealing machines.