Disposable diaper

Provided is a disposable diaper capable of suppressing leakage in the width direction of a liquid. A disposable diaper includes a ventral portion, a dorsal portion, and an absorbent body including anabsorbent body. The absorbent body includes a super absorbent polymer including a crotch region, a back-side region overlapping the back-side portion in the thickness direction, and a ventral-side region overlapping the ventral-side portion in the thickness direction. At least one of the dorsal region and the ventral region includes a low-weight-per-unit-area region in which the weight per unit area of the super absorbent polymer is lower than the weight per unit area of the crotch region. The absorbent body includes a pair of side sheets. Each of the pair of side sheets has: a fixing region that is fixed to the surface of the absorbent body; and a leak-proof wall having an end edge on the outer side in the width direction fixed to the surface of the absorbent body and an end edge on the inner side in the width di