A method for manufacturing an underpants-type disposable diaper comprising: an outer body that is formed by joining both side parts of a ventral side outer body and both side parts of a dorsal side outer body; and an inner body that has a front part joined to a width-direction central area of the ventral side outer body and a back part joined to a width-direction central area of the dorsal side outer body respectively and passes through a crotch portion of a wearer, the ventral side outer body and the dorsal side outer body being not continued but separated at a crotch side, wherein a belt-like continuous first sheet material is supplied in a direction of continuity thereof, resilient and elastic members for imparting elasticity to the ventral side outer body and the dorsal side outer body are disposed on the first sheet material, a belt-like continuous second sheet material is supplied in a direction of continuity thereof on the resilient and elastic members in the first sheet material to sandwich the resilient and elastic members between the first sheet material and the second sheet material, and overlapping areas of the first sheet material and the second sheet material are not continuously joined together at the ends in the CD direction thus forming non-joined portions extending along the MD direction, the first sheet material and the second sheet material being joined together at the area between the non-joined portions in the CD direction by a hot-melt adhesive to form a belt-like continuous elastic belt, the elastic belt is cut in the middle of a CD direction thereof at a joined position of the first sheet material and the second sheet material to form a pair of divided elastic belts (12b, 12f), and the CD direction positions of these divided elastic belts are exchanged or the divided elastic belts are vertically reversed respectively so that the CD direction central edges of the divided elastic belts are positioned outside in the CD direction and the CD direction outer edges of the same are positioned on the CD direction central side, and the diaper is manufactured such that one of the pair of divided elastic belts is set as the ventral side outer body and the other is set as the dorsal side outer body, and the waist edges of the ventral side outer body and the dorsal side outer body are formed from the cut edges of the divided elastic beltswhereby the first sheet material and the second sheet material are joined together right up to the edges, and the non-joined portions of the elastic belt are positioned at the leg-opening end portions of the ventral side outer body and the dorsal side outer body. an outer body that is formed by joining both side parts of a ventral side outer body and both side parts of a dorsal side outer body; and an inner body that has a front part joined to a width-direction central area of the ventral side outer body and a back part joined to a width-direction central area of the dorsal side outer body respectively and passes through a crotch portion of a wearer, the ventral side outer body and the dorsal side outer body being not continued but separated at a crotch side, wherein a belt-like continuous first sheet material is supplied in a direction of continuity thereof, resilient and elastic members for imparting elasticity to the ventral side outer body and the dorsal side outer body are disposed on the first sheet material, a belt-like continuous second sheet material is supplied in a direction of continuity thereof on the resilient and elastic members in the first sheet material to sandwich the resilient and elastic members between the first sheet material and the second sheet material, and overlapping areas of the first sheet material and the second sheet material are not continuously joined together at the ends in the CD direction thus forming non-joined portions extending along the MD direction, the first sheet material and the second sheet material being joined together at the area between the non-joined portions in the CD direction by a hot-melt adhesive to form a belt-like continuous elastic belt, the elastic belt is cut in the middle of a CD direction thereof at a joined position of the first sheet material and the second sheet material to form a pair of divided elastic belts (12b, 12f), and the CD direction positions of these divided elastic belts are exchanged or the divided elastic belts are vertically reversed respectively so that the CD direction central edges of the divided elastic belts are positioned outside in the CD direction and the CD direction outer edges of the same are positioned on the CD direction central side, and the diaper is manufactured such that one of the pair of divided elastic belts is set as the ventral side outer body and the other is set as the dorsal side outer body, and the waist edges of the ventral side outer body and the dorsal side outer body are formed from the cut edges of the divided elastic beltswhereby the first sheet material and the second sheet material are joined together right up to the edges, and the non-joined portions of the elastic belt are positioned at the leg-opening end portions of the ventral side outer body and the dorsal side outer body.