On the back sheet side, back-side recessed portions recessed toward the top sheet are provided in a surface of the absorber of the disposable diaper. The back-side recessed portions include multiple grooves, which are continuous in the longitudinal direction L of the absorber. The back-side recessed portions is visible from an outside of the back sheet in a state before the disposable diaper is used, and when the absorber absorbs liquid, the depth D of the back-side recessed portions is made smaller than that before the absorber absorbs liquid. When the hydrophilic fiber and the particulate SAP swells, and thereby the absorber expands in at least the thickness direction thereof, the back-side recessed portions seems to disappear from the outside.
