A disposable diaper is provided, including an absorber, a top sheet disposed to cover the upper surface of the absorber and at least partially formed of a liquid permeable material, a back sheet disposed to cover the lower surface of the absorber and formed of a liquid impermeable material, and a skin contact sheet disposed above the top sheet and formed with a stool passing opening capable of passing a stool therethrough. The stool passing opening is formed into such a shape that a posterior region posterior to a centerline in the anteroposterior direction of the stool passing opening is smaller in the opening area than an anterior region anterior to the centerline.