In a disposable diaper, a back waist region includes a belt region extending in a transverse direction on a skin-facing surface and a downward openable pocket facing, in a front-back direction, a central sub-region in the transverse direction of the belt region. The pocket is defined by a pocket outside wall facing the middle portion in the front-back direction and extending upward from the crotch region, a pocket inside wall facing the pocket outside wall and the belt region, respectively, in the front-back direction, and being continuous with the pocket outside wall through a folded portion and extending downward from the fold line so as to become continuous with the pocket inside wall of the middle portion in the belt region, and both pocket lateral portions formed from the respective lateral portions of the inside and outside walls, and tucked inward in the transverse direction.