[Problem] To prevent lateral tearing of a side seal part, which arises in a sheet bonding part. [Solution] Stretching regions A2, A3 of exterior bodies 12F, 12B comprise a plurality of long, narrow elastic stretching members 19, which are positioned between two sheet layers 12S, 12H in the fore-aft direction with spaces between said stretching members, said stretching members extending in the width direction. The elastic stretching members 19 have anchor end parts 19f whereby both end parts of the elastic stretching members 19 in the width direction are anchored to the two sheet layers 12S, 12H. The elastic stretching members 19 are not anchored to the two sheet layers 12S, 12H between the anchor end parts 19f. In the region between the anchor end parts 19f, the two sheet layers 12S, 12H are fuse bonded, at sites between the elastic stretching members 19 which are adjacent in the fore-aft direction, by sheet bonding parts 20 which are continuous in the width direction. In each of regions 13A, 13B into which a side seal part 13 is bisected in the width direction, fuse bonding parts 13s are disposed intermittently and in a regular pattern in the longitudinal direction. The peel strength of the first region 13A is lower than the peel strength of the second region 13B.Le problème décrit par la présente invention consiste à empêcher le déchirement latéral d'une partie étanchéité latérale, se produisant dans une partie de collage de feuilles. La solution de l'invention porte sur des régions extensibles (A2, A3) de corps extérieurs (12F, 12B) comprenant une pluralité d'éléments extensibles élastiques étroits et longs (19), qui est positionnée entre deux couches de feuille (12S, 12H) dans le sens avant-arrière, des espaces étant présents entre lesdits éléments extensibles, lesdits éléments extensibles s'étendant dans le sens de la largeur. Les éléments extensibles élastiques (19) comprennent des parties extrémité d'ancrage (19f) grâce auxquelles les deux parties extrémité d
