The displacement mechanism includes: an urging mechanism that urges an anvil roller toward an ultrasonic horn in such a manner that output surfaces and a welding surface move closer in the normal direction thereof； and a pressed member that has guide surfaces against which the outer surface of the anvil roller, positioned within non-welding areas, are pressed by an urging force of the urging mechanism, the pressed member being fixed to a sheet holding roller in a state where a pressed surface is disposed within the width-direction range of a slit. In response to the movement of the anvil roller from a welding area to the non-welding areas, the guide surfaces of the pressed member guide the anvil roller in a direction in which the output surfaces and the welding surface move away from each other.
