An underpants-type disposable diaper comprising: an outer member (12F, 12B) forming at least lower torso portions of a front body and a back body; an inner member attached to the outer member (12F, 12B) so as to extend from the front body to the back body and including an absorber; a waist opening; and a pair of left and right leg openings, a waist portion of the outer member (12F, 12B) including: a plurality of elongated waist elastic members disposed in a width direction at intervals; a waist inner sheet layer facing insides of the waist elastic members; and a waist outer sheet layer facing outsides of the waist elastic members, the waist elastic members being bonded to the waist inner sheet layer and the waist outer sheet layer via a hot melt adhesive, wherein the waist portion has a first portion closer to the waist opening than an intermediate portion in a front-back direction and a second portion opposite thereto, and the first portion and the second portion each have at least one of the waist elastic members, wherein the position of the boundary between the first portion and the second portion may be different or the same between the inside and the outside of the waist portion, the first portion includes an over sheet layer folded back at an edge of the waist opening from an outside of the waist outer sheet layer and extending to an inside of the waist inner sheet layer, the over sheet layer is formed of a sheet material having a portion folded back at an edge of the waist opening from a position outside the waist elastic member in the second portion and extending to a position inside the waist elastic member in the second portion, in the first portion, the waist elastic member is not fixed to the sheet material, and in the second portion, the waist elastic member is fixed to the sheet material, and the sheet material is contracted in a width direction together with the waist elastic member. an outer member (12F, 12B) forming at least lower torso portions of a front body and a back body; an inner member attached to the outer member (12F, 12B) so as to extend from the front body to the back body and including an absorber; a waist opening; and a pair of left and right leg openings, a waist portion of the outer member (12F, 12B) including: a plurality of elongated waist elastic members disposed in a width direction at intervals; a waist inner sheet layer facing insides of the waist elastic members; and a waist outer sheet layer facing outsides of the waist elastic members, the waist elastic members being bonded to the waist inner sheet layer and the waist outer sheet layer via a hot melt adhesive, wherein the waist portion has a first portion closer to the waist opening than an intermediate portion in a front-back direction and a second portion opposite thereto, and the first portion and the second portion each have at least one of the waist elastic members, wherein the position of the boundary between the first portion and the second portion may be different or the same between the inside and the outside of the waist portion, the first portion includes an over sheet layer folded back at an edge of the waist opening from an outside of the waist outer sheet layer and extending to an inside of the waist inner sheet layer, the over sheet layer is formed of a sheet material having a portion folded back at an edge of the waist opening from a position outside the waist elastic member in the second portion and extending to a position inside the waist elastic member in the second portion, in the first portion, the waist elastic member is not fixed to the sheet material, and in the second portion, the waist elastic member is fixed to the sheet material, and the sheet material is contracted in a width direction together with the waist elastic member.