The invention is a disposable diaper (1) provided with: an absorbent body (2) comprising an absorbent (23) and an outer composite sheet (22) and expandable side panels (3). The side panels (3) have two sheets (31, 32) and an elastic member (33), and have fastening tape (4) at the leading edge (3a). The outer composite sheet (22) has an anti-leak sheet (22a) and an outer nonwoven fabric (22b) that is joined thereto by means of an outer adhesive layer (61). The side panels (3) have main body side and base end side adhesive layers (35, 36). The base end (3b) is reinforced by means of a reinforcing adhesive layer (63) that overlaps or is continuous with the adhesive layer (35), and is joined to the outer composite sheet (22) by a connecting adhesive layer (62). The adhesive layers (35) are formed, at a distance from each other, on the outside of the adhesive layer (61) in the diaper width direction, and the adhesive layers (35, 63, 62, 61) are provided so that there are no gaps in the diaper width direction.
