To provide a diaper for a low body weight infant, making a belt member hardly come off from a body part at the time of attachment.SOLUTION: A diaper (1) for a low body weight infant comprises an exterior sheet (24) arranged at a non-skin side of an absorber (21), and a belt member (30) including locking members (31) at one side and the other side in the width direction. The belt member (30) is locked to a non-skin side of the exterior sheet (24) by the locking member (31) at the one side, and an additional connection part (70) for peelably connecting a part of the belt member to the exterior sheet (24) is provided in a region at the one side of the belt member (30).SELECTED DRAWING: Figure 5【課題】着用時にベルト部材が本体部から離脱し難い低体重児用のおむつを提供する。【解決手段】吸収体（２１）よりも非肌側に配された外装シート（２４）と、幅方向の一方側及び他方側に係止部材（３１）を備えたベルト部材（３０）と、を有する低体重児用おむつ（１）であって、前記ベルト部材（３０）は、前記一方側の前記係止部材（３１）によって前記外装シート（２４）の非肌側に係止されており、前記ベルト部材（３０）の前記一方側の領域には、前記ベルト部材の一部を剥離可能に前記外装シート（２４）と接合する追加接合部（７０）が設けられている。【選択図】図５
