A disposable diaper (10) includes a pair of fastening tapes (90) disposed on product widthwise outer ends of the back lower-torso region and configured to be fastened to the front lower-torso region, and a waist elastic sheet extending bilaterally from the center in the product width direction of the disposable diaper and being elastically extensible in the product width direction. The waist elastic sheet includes a back waist elastic sheet disposed at a back end (10R) of the diaper. When the disposable diaper is in a relaxed state, the back end (10R) of the disposable diaper has a curved shape in which the product widthwise center is recessed inward in the product longitudinal direction from the product widthwise outer ends.
