This disposable diaper (10) is provided with: a liquid-impermeable leakage-preventing sheet (55) provided at the non-skin-contacting surface side of an absorbent main body (15) and a pair of leg-encircling extending/contracting sections (100). The leakage-preventing sheet (55) has: an overlapping region (R1) overlapping the leg-encircling extending/contracting sections (100) in a plan view of the disposable diaper (10) and a non-overlapping region (R2) that is positioned to the outside of in the product lengthwise direction (L) of the overlapping region (R1) and that does not overlap the leg-encircling extending/contracting sections (100). The overlapping region (R1) is formed at the portion at which the distance in the product widthwise direction (W) between one of the leg-encircling extending/contracting sections (100) and the other of the leg-encircling extending/contracting sections (100) becomes the narrowest and at the central section in the product lengthwise direction (L), and becomes narrower towards the outside in the product lengthwise direction (L).Cette couche-culotte jetable (10) est pourvue : dune feuille anti-fuite imperméable aux liquides (55) prévue au niveau du côté surface non en contact avec la peau dun corps principal absorbant (15) et dune paire de sections dextension/contraction encerclant les jambes (100). La feuille anti-fuite (55) présente : une région de chevauchement (R1) chevauchant les sections dextension/contraction encerclant les jambes (100) dans une vue en plan de la couche-culotte jetable (10) et une région de non-chevauchement (R2) qui est positionnée à lextérieur dans le sens de la longueur du produit (L) de la région de chevauchement (R1) et qui ne chevauche pas les sections dextension/contraction encerclant les jambes (100). La région de chevauchement (R1) est formée au niveau de la partie au niveau de laquelle la distance dans le sens de la largeur (W) du produit entre lune des sections dextension/contraction encerclant les
