A disposable diaper has a pair of first surface fastener members supported by a rear flap of a diaper body and a second surface fastener member supported by a front flap of the diaper body. The first and second surface fastener members have first and second engaging elements; the first and/or second engaging elements are made of water-soluble resin. After approximately 1/3 to 2/5 of the diaper body on the side of the rear flap is folded inwardly, the diaper body is wound into a roll toward the front flap, and then the water-soluble resin of the first and/or second engaging elements is dissolved with water. Then the first surface fastener members are pressed against the second surface fastener member to fasten the diaper body in roll as waste.