[Problem] To provide a disposable diaper that can prevent leakage while ensuring the fit between the crotch of the body and the fit of the buttocks. The disposable diaper (10) is provided with: an absorbent core (31) arranged at least in the crotch region, and an outer side which is arranged on both outer sides of the center of the absorbent core in the widthwise direction and extends in the front-rear direction Right hip extension (41). The absorbent core has the aforementioned narrow portion (35) having a shorter length in the lateral direction than the front portion and the rear portion. At least a part of the crotch expansion-contraction part is arrangepositioned rather than the outer edge of the absorbent core in the width direction in the narrow part. The rear end edge (41R) of the lower crotch expansion portion (41) is arranged closer to the front side than the rear end edge (35R) of the narrow portion (35).[課題] 提供既確保對身體的胯間的貼合性，又確保對臀部的貼合性，而可抑制洩漏的用後即棄式紙尿布。用後即棄式紙尿布(10)具備有：至少被配置在胯下域的吸收芯(31)、以及被配置在吸收芯的寬邊方向的中心的兩外側，且朝前後方向延伸的一對的胯下伸縮部(41)。吸收芯具有前述寬邊方向的長度較前部及後部更短的狹窄部(35)。胯下伸縮部的至少一部分在狹窄部被配置在較吸收芯的外側緣更靠寬邊方向的內側。胯下伸縮部(41)的後端緣(41R)被配置在較狹窄部(35)的後端緣(35R)更靠前側。
