A disposable diaper includes: a main body having a liquid-permeable topsheet, a liquid-impermeable outer sheet an absorber provided between the topsheet and the outer sheet, and a gather. The gather includes a plurality of elastic members arranged in a width direction outboard of the absorber. The elastic members are fixed to the gather in a state where the elastic members are stretched in a longitudinal direction. A side flap is located in one of end portions of the main body in the longitudinal direction and projects outwardly beyond at least one of end portions of the main body in the width direction. A joint portion joins the side flap and the main body. In a spread-out state of the disposable diaper, an outermost elastic member among the elastic members is arranged outboard of the joint portion in the width direction.
