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; and joining the first sheet layer and the second sheet layer together with a number of joints directly or through the resilient film by melting the resilient film with ultrasonic fusion energy applied by a thermal fusion device from an outside of the first sheet layer and an outside of the second sheet layer to a number of joint regions 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, a counter roll is arranged to face the anvil roll, the counter roll is a nip roll which constitutes a nip stage together with the anvil roll, the resilient film is supplied around the counter roll so as to be supplied around the anvil roll through the nip stage, while the anvil roll is accelerated to be faster than the counter roll in peripheral speed to stretch the resilient film and additionally a group of the protruding portions of the anvil roll and the ultrasonic horn performs the joining, wherein a distance between the nip stage and a position at which the resilient film separates form the anvil roll is 250 mm or less. 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; and joining the first sheet layer and the second sheet layer together with a number of joints directly or through the resilient film by melting the resilient film with ultrasonic fusion energy applied by a thermal fusion device from an outside of the first sheet layer and an outside of the second sheet layer to a number of joint regions 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, a counter roll is arranged to face the anvil roll, the counter roll is a nip roll which constitutes a nip stage together with the anvil roll, the resilient film is supplied around the counter roll so as to be supplied around the anvil roll through the nip stage, while the anvil roll is accelerated to be faster than the counter roll in peripheral speed to stretch the resilient film and additionally a group of the protruding portions of the anvil roll and the ultrasonic horn performs the joining, wherein a distance between the nip stage and a position at which the resilient film separates form the anvil roll is 250 mm or less.