Elastic sheet, underpants-type absorbent article, and method for manufacturing elastic sheet

A method for manufacturing a stretchable sheet that includes a first sheet, a second sheet joined to the first sheet by welded portions, and an elastic member that is disposed between the first sheet and the second sheet and that stretches and contracts in a continuous direction in which the elastic member extends, wherein the welded portions are disposed on both sides of the elastic member in an intersecting direction intersecting with the continuous direction, welded portion pairs are disposed in which the elastic member in a state of contracting in the continuous direction is sandwiched and restrict a position of the elastic member in the intersecting direction with respect to the first sheet and the second sheet, the method comprising:

• transporting a continuous body of the first sheet, a continuous body of the second sheet, and a continuous body of the elastic member, which are continuous in the continuous direction, in a direction of transport corresponding to the continuous direction and intersecting the intersecting direction;
• and
• joining the continuous body of the first sheet and the continuous body of the second sheet, by arranging continuous bodies of the elastic members side by side in the intersecting direction between the continuous body of the first sheet and the continuous body of the second sheet, and by subsequently forming the welded portion pairs such that each of the continuous bodies of the elastic members is sandwiched from both sides in the intersecting direction, wherein
• the continuous bodies of the elastic members are in a stretched state in the direction of transport,
• the joining of the continuous body of the first sheet and the continuous body of the second sheet comprises when forming the welded portion pairs:
• forming a damaged portion where a part of a surface of the continuous body of the elastic member is damaged;
• and
• joining the continuous body of the first sheet and the continuous body of the second sheet such that the damaged portion is arranged between a first welded portion pair and a second welded portion pair that are adjacent to each other in the continuous direction.