In the absorbent article which has a side flap which can be expanded-contracted, it suppresses that the edge part of a back side falls down to the non-skin side, and prevents excrement from leaking from a back. The absorbent article (1) includes an absorbent main body (AB) including the absorbent body 4 and a pair of side flaps (SF, SF) extending outward from both ends in the width direction of the absorbent main body. The side flap includes a sheet-like stretchable member (12) that can be stretched in the width direction, sheet members (7a, 7b) that are respectively laminated on both sides in the thickness direction of the stretchable member, and an outer side in the width direction of the stretchable member. A locking member (8) connected to the end and extending outward. Each of the pair of side flaps is joined to the skin side of the absorbent main body in the thickness direction. In the longitudinal direction, the end on the back side of the absorbent body is located on the back side with respect to the imaginary line connecting the ventral side edges of the locking member in the width direction.伸縮可能なサイドフラップを有する吸収性物品において、背側の端部が非肌側に倒れることを抑制し、排泄物が背中から漏れることを防止する。吸収性物品（１）は、吸収体４を含む吸収性本体（ＡＢ）と、吸収性本体の幅方向の両端部から外側に延出する一対のサイドフラップ（ＳＦ、ＳＦ）と、を備える。サイドフラップは、幅方向に伸縮可能なシート状の伸縮部材（１２）と、伸縮部材の厚さ方向の両面にそれぞれ積層されたシート部材（７ａ、７ｂ）と、伸縮部材の幅方向の外側の端部に接続され、外側に延出する係止部材（８）と、を備える。一対のサイドフラップの各々は、厚さ方向において、吸収性本体よりも肌側に接合されている。長手方向において、吸収体の背側の端部は、係止部材の腹側の端縁同士を幅方向に結ぶ仮想線よりも背側に位置する。
