A disposable diaper (1) provided with a waist opening (WO) and a pair of leg openings (LO), wherein a composite stretchable material (5) is positioned at least in side parts (WPE) of a waist part (WP) that is located between the waist opening and the leg openings. The composite stretchable material comprises first and second non-woven fabric sheet parts (6U, 6L) and an elastic member (7) interposed therebetween. Each of the first and second non-woven fabric sheet parts comprises a plurality of concave/convex areas (41) consisting of concave portions (51) and convex portions (53), said concave portions and convex portions being alternately repeated along the lateral direction (L) and extending in the longitudinal direction (T), and at least one non-concave/convex area (43) for separating the concave/convex areas from each other in the longitudinal direction. The first and second non-woven fabric sheet parts are stacked so that the concave/convex areas are positioned adjacent to each other and the non-concave/convex areas are separated from each other and bonded together with an adhesive that is applied to the elastic member.
