PROBLEM TO BE SOLVED: To provide an underpants-type disposable diaper having external appearance like an underwear and excellent in wear feeling while including a side seal part having seal strength sufficient for practical use, and excellent operability.SOLUTION: A thickness 4W of a side seal part 4 is large compared to a thickness of a part excluding the side seal part 4 of each of a ventral part F and a back side part R constituting it. The ventral part F and the back side part R constituting the side seal parts 4 are each constituted by including a laminated structure of a plurality of sheet-like members. Among the plurality of sheet-like members, a melting point of constituent fibers of at least one sheet-like member is different from a melting point of constituent fibers of the other sheet-like member. The laminated structure of the ventral part F and the back side part R includes a low melting innermost layer-type laminated structure 41 where an innermost layer comprises a low melting sheet-like member 37 having the lowest melting point among the plurality of sheet-like members. The side seal part 4 is formed by a laser seal method.COPYRIGHT: (C)2015,JPO&INPIT【課題】実用上十分なシール強度を有し且つ操作性に優れるサイドシール部を備えながらも、下着のような外観を有し、着用感に優れるパンツ型使い捨ておむつを提供すること。【解決手段】サイドシール部4の厚み4Wは、これを構成する腹側部F及び背側部Rそれぞれの該サイドシール部4以外の部分の厚みに比して大きい。サイドシール部4を構成する腹側部F及び背側部Rは、それぞれ、複数のシート状部材の積層構造を含んで構成されており、複数の該シート状部材のうち、少なくとも一つのシート状部材の構成繊維の融点は、他のシート状部材の構成繊維の融点と異なる。腹側部F及び背側部Rの前記積層構造は、それぞれ、最内層が複数の前記シート状部材のうち最も前記融点の低い低融点シート状部材37からなる、低融点最内層型積層構造41を含む。サイドシール部4は、レーザーシール方式によって形成されている。【選択図】図4
