PROBLEM TO BE SOLVED: To provide an underpants type disposable diaper with high visibility by visual observation of a side seal part, and a method for manufacturing the same.SOLUTION: A diaper 50B in this invention is an underpants type disposable diaper which includes an exterior body 3 forming an outer surface, and in which a pair of side seal parts 4, 4, a waist opening part 8, and a pair of leg opening parts 9, 9 are formed by connecting both right and left side edge parts of the exterior body 3 in a front body F to both right and left side edge parts of the exterior body 3 in a rear body R. The side seal part 4 has a sealed edge part 41 in which an edge part 3F of the exterior body in the front body and an edge part 3R of the exterior body in the rear body are joined together at a continuous linear fusion part extending in a longitudinal direction of the side seal part, and a non-sealed part 42 in which the edge part 3F of the exterior body in the front body and the edge part 3R of the exterior body in the rear body face each other in a non-joined state partially.【課題】サイドシール部の目視による視認性が高いパンツ型使い捨ておむつ及びその製造方法を提供すること。【解決手段】本発明のおむつ５０Ｂは、外面を形成する外装体３を備え、前身頃Ｆにおける外装体３の左右両側縁部と後身頃Ｒにおける外装体３の左右両側縁部とが接合されて一対のサイドシール部４，４、ウエスト開口部８及び一対のレッグ開口部９，９が形成されているパンツ型使い捨ておむつであり、サイドシール部４は、前身頃における外装体の縁部３Ｆと後身頃における外装体の縁部３Ｒが、サイドシール部の長手方向に延在する連続線状の融着部で結合したシール縁部４１を有すると共に、前身頃における外装体の縁部３Ｆと後身頃における外装体の縁部３Ｒが、非結合状態で対向する非シール部４２を部分的に有している。【選択図】図９
