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).用後即棄式紙尿布(10)是具備有:比吸收性本體(15)更被設置在非肌膚抵接面側的不透液性的防漏薄片(55);以及一對的腿圍伸縮部(100)。防漏薄片(55)在用後即棄式紙尿布(10)的俯視觀看,具有:與腿圍伸縮部(100)重疊的重複區域(R1);以及位在重複區域(R1)的製品長方向(L)外側,沒有與腿圍伸縮部(100)重疊的非重複區域(R2)。重複區域(R1)是腿圍伸縮部(100)的一方與腿圍伸縮部(100)的另一方之間的製品寬幅方向(W)的距離被設的最狹窄的部分,且被形成在製品長方向(L)的中央部,並且愈朝向製品長方向(L)外側變的愈窄。20‧‧‧前腰圍部25‧‧‧胯下部30‧‧‧後腰圍部35‧‧‧腿圍凹部55‧‧‧防漏薄片100‧‧‧腿圍伸縮部110‧‧‧凸部200‧‧‧伸縮薄片R1‧‧‧重複區域R2‧‧‧非重複區域
