An expandable/contractable sheet (31), in which a plurality of elastic members (35) are positioned between a first sheet (32) and a second sheet (33) that are joined by a plurality of weld sections (50), has a first weld section (51) and a third weld section (53) on an upper side of one elastic member (35) and has a second weld section (52) and a fourth weld section (54) on a lower side of the one elastic member (35). The one elastic member (35) is attached by being clamped in a vertical direction by the first weld section (51) and the second weld section (52) and being clamped in the vertical direction by the third weld section (53) and the fourth weld section (54), the first weld section (51) and the third weld section (53) have portions that overlap in the vertical direction, and the lower edge position of the first weld section (51) and the lower edge position of the third weld section (53) are not aligned in the vertical direction.
