To acquire a stretchable sheet having air permeability due to the presence of through-holes, with no hole formed through outer layers.There are provided: interposing a resilient film (30) that stretches and contracts, in a stretched state between a first sheet layer (21) having no elasticity and a second sheet layer (22) having no elasticity； and joining the first sheet layer (21) and the second sheet layer (22) together with a number of joints directly or through the resilient film by melting the resilient film (30) with ultrasonic fusion energy applied by a thermal fusion device from the outside of the first sheet layer (21) and the outside of the second sheet layer (22) to a number of joint regions with intervals, during the interposing. The resilient film (30) is supplied around a counter roll (63) so as to be supplied around the anvil roll (60), and the anvil roll (60) is accelerated to be faster than the counter roll (63) in peripheral speed to stretch the resilient film (30).
