A form-fill-seal machine (1) has a forming structure, a vertical seal structure, and a clamp fixing mechanism (18). The forming structure has a support frame (33), a tube (31), a sailor collar-shaped unit (32), and an anvil (51). The tube (31) is fixed to the support frame (33). The sailor collar-shaped unit (32) is fixed to the support frame (33), and wraps a sheet-shaped film around the tube (31) so that two ends thereof overlap. The anvil (51) is fixed to the tube (31). The vertical seal structure has an oscillator (50). The oscillator (50) generates ultrasonic waves in order to seal overlapping portions of two ends of the film, being conveyed through the intervening gap with the anvil (51), in a vertical direction. The clamp fixing mechanism (18) fixes the forming structure and the vertical seal structure in fixed positions relative to one another.