To provide an underpants type absorbent article in which fitting property of an absorbent core is improved in a crotch part.SOLUTION: An underpants type absorbent article (1) has: an absorbent body (10) which comprises an absorbent core (11) disposed along a vertical direction and is bent from front to rear at a lower end in the vertical direction； and a crotch member (23) which is laminated on a non-skin side of the absorbent core (11) in a crotch part located in a crotch of a wearer when it is worn and has a crotch elastic region (23 s) extending and contracting along the vertical direction. The crotch region of the absorbent core (11) is provided with a crotch low basis weight region (36) having a lower average basis weight than a surrounding region. The crotch low basis weight region (36) has a laterally long part (36w) along a lateral direction. At least a part of the laterally long part (36w) overlaps with the crotch elastic region (23 s).SELECTED DRAWING: Figure 5【課題】股間部において吸収性コアのフィット性を向上させたパンツ型吸収性物品を提供する。【解決手段】上下方向に沿って配置された吸収性コア（１１）を備え、上下方向の下端部にて前後に折り曲げられた吸収性本体（１０）と、着用時に着用者の股下に位置する股下部において、吸収性コア（１１）よりも非肌側に積層され、上下方向に沿って伸縮する股下伸縮領域（２３ｓ）を有する股下部材（２３）と、を有するパンツ型吸収性物品（１）であって、吸収性コア（１１）の股下部には、周囲の領域よりも平均坪量が低くなっている股下低坪量領域（３６）が設けられており、股下低坪量領域（３６）は、左右方向に沿った横長部（３６ｗ）を有し、横長部（３６ｗ）のうち少なくとも一部が、股下伸縮領域（２３ｓ）と重複している。【選択図】図５
