A disposable diaper improved so that the wearer's skin can be reliably protected from being soiled with feces. A chassis constituting the diaper includes a spacer sheet attached to an inner sheet of the chassis. The spacer sheet has a front end zone and a rear end zone fixed to the inner sheet and an intermediate zone left free from the inner sheet. The intermediate zone is formed with an opening shaped so as to describe a circular arc which is convex forward. Along the opposite side edges of the opening, the spacer sheet is provided with elastic members extending in the length direction of the diaper and attached thereto in a stretched state in the direction. These elastic members extend forward with respect to the diaper along the peripheral edge of the opening so as to get close to a center line bisecting a width of the diaper.