Abstract: A method of bundling bags by heat-adhesion comprising the steps of: making holes in bags made of heat-adhesive material; inserting guide rods into the holes of the bags to stack the bags at the correct position; pressing a heated thermal cutter against one end surface of the stacked bags to bond them together by heat-adhesion. Said guide rods are moved in synchronism with the feeding of the bag so as to be inserted into the holes formed in the bag. Said guide rods are inserted vertically slidable through bag holding cylinders having vertical grooves, the guide rods are provided at their top ends with arrows, those rear ends of the arrows that project from the side of the guide rods are hooked on the peripheral edges of the holes of the bag, and as the guide rods are lowered, the rear ends of the arrows are slid downwardly through the grooves of the bag holding cylinders to force the bag down the cylinders.