PURPOSE: To efficiently perform the heat fusion-bonding work of an opening of a synthetic resin packaging bag, packaging pack, etc., by pivotally providing the base end of a clamp lever to be cranked on a rotary board, pivotally providing the base end of a swing arm at the other end of the lever, and securing the other end of the arm to a rocker.

CONSTITUTION: An opening of a packaging bag or a packaging pack, etc., in which content is filled, is inserted between an opened heater H and a pressing pad P. When a geared motor M is driven, rotary boards 6, 7 are rotated through a driver gear 3 and a driven gear 5. Then, crank levers 10, 11 pivotally provided at the boards 6, 7 are cranked, the front end of a rocker 13 is pressed from above to below through swing arms 14, 15, the opening of the bag, the pack, etc., disposed on the heater H is automatically pressed in contact by the pad P of the rocker 13 side, the contact state is held for short time, it is heat fusion- bonded, the heater H is turned OFF, controlled to be cooled, thereby securing the opening of the bag, the pack, etc.