Method of manufacturing stretchable sheet

A method of manufacturing a stretchable sheet that stretches and contracts, the method comprising:

• interposing a resilient film that stretches and contracts, in a stretched state between a first sheet layer having no elasticity and a second sheet layer having no elasticity, the first sheet layer being supplied in a machine direction, the second sheet layer being supplied in the machine direction, the resilient film being supplied in the machine direction;
• and
• joining the first sheet layer and the second sheet layer together at a number of joints directly or through the resilient film by melting the resilient film with thermal fusion energy applied by a thermal fusion device from an outside of the first sheet layer and an outside of the second sheet layer with intervals, in a state where the resilient film has been interposed in the stretched state between the first sheet layer and the second sheet layer, during the interposing,
• wherein the thermal fusion device includes an anvil roll and an ultrasonic horn,
• the anvil roll includes a number of protruding portions formed with intervals in a roll length direction and in an outer circumferential direction on an outer surface,
• the number of the protruding portions and the ultrasonic horn perform the joining,
• the anvil roll faces a nip roll,
• the resilient film and the second sheet layer are inserted into a nip roll stage including the nip roll and the anvil roll facing the nip roll, the resilient film is supplied around the nip roll, the resilient film and the second sheet layer are supplied around the anvil roll through nips of the nip roll stage,
• the anvil roll and the ultrasonic horn join the first sheet layer, the resilient film, and the second sheet layer together, the ultrasonic horn is arranged to face the anvil roll, and
• a through-hole is formed at least at a boundary portion in the machine direction between the resilient film and each of the joints, with the first sheet layer and the second sheet layer retained, no hole is formed over entirety of each of joint regions during the joining.