PROBLEM TO BE SOLVED: To prevent appearance from becoming deteriorated by a corner on a leg opening side of a side edge of a buttock cover part in an underpants type disposable diaper of an external two-division type.SOLUTION: In an underpants type disposable diaper which is separately provided with a front side exterior body 12F and a back side exterior body 12B and in which the front side exterior body 12F and the back side exterior body 12B are separate in a back and forth direction LD in the middle of the back and forth direction LD, the back side exterior body 12B has a buttock cover part C extending more to a center side in the back and forth direction than a side seal part 12A. A back and forth direction dimension of the side edge of the buttock cover part C is 0.9 to 1.1 multiples of a width direction dimension W3 from the side edge of the back side exterior body 12B to the side edge on the center side in the width direction of the side seal part 12A.SELECTED DRAWING: Figure 1COPYRIGHT: (C)2018,JPO&INPIT【課題】外装二分割タイプのパンツタイプ使い捨ておむつにおいて、臀部カバー部の側縁の脚開口側の角が目立つことにより外観が悪化するのを防止する。【解決手段】上記課題は、前側外装体１２Ｆ及び後側外装体１２Ｂとを別々に備え、これら前側外装体１２Ｆ及び後側外装体１２Ｂが前後方向ＬＤ中間で前後方向ＬＤに離間したパンツタイプ使い捨ておむつにおいて、後側外装体１２Ｂはサイドシール部１２Ａよりも前後方向中央側に延び出た臀部カバー部Ｃを有しており、臀部カバー部Ｃの側縁の前後方向寸法は、後側外装体１２Ｂの側縁からサイドシール部１２Ａの幅方向中央側の側縁までの幅方向寸法Ｗ３の０．９～１．１倍であることにより解決される。【選択図】図１
