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 30 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. A through-hole (31) is formed through at least a boundary portion in a direction of the stretching between the resilient film (30) and each of joints (40), with the first sheet layer (21) and the second sheet layer (22) retained, no hole being formed over the entirety of each of the joint regions.
