Abstract: Disclosed is a disposable diaper including a pair of leak-proof cuffs (6) provided respectively to both lateral sides of an absorbent assembly (5) along the longitudinal direction. Each leak-proof cuff (6) includes: an inwardly-oriented portion (63) wherein a leak-proof-cuff-forming sheet material (61) is arranged from a lateral side edge (43) of an absorbent core toward the absorbent member's inner side in the width direction; a fold-back portion (64) where the sheet material (61) is folded back toward the absorbent member's outer side in the width direction, the fold-back portion being located above the absorbent member (4); and an outwardly-folded portion (65) ranging from the fold-back portion (64) to a free end (6b) of the leak-proof cuff. The outwardly-folded portion (65) has a length, in the width direction, that is longer than the length of the inwardly-oriented portion (63), and a plurality of elastic members (62) are fixed in a stretched state to the outwardly-folded portion.