[Problem] A disposable diaper for low-weight children in which the member is not easily detached from the main body portion when worn is provided. [Solution] A low-weight baby diaper (1) having an absorbent body (21) having at least an absorbent core (21a) and an outer sheet disposed on the non-skin side of the absorbent body (21) (24)； and the belt member (30), wherein the belt member (30) is provided with a locking member (31A, 31B) on one side and the other side in the longitudinal direction of the belt member (30), and the belt member ( 30) The outer side end (24leo) of the outer sheet (24) in the longer side direction is further inside by the locking member (31A) on one side, and the outer sheet (24) in the thickness direction is locked In the non-skin side, the outer end (21leo) of the absorbent core (21a) is in the longitudinal direction, and is closer to the outer end (24leo) of the outer sheet (24) and the outer end of the locking member (31A) on the one side. The middle of (31Aleo) is located on the inside.[課題]提供一種穿用時，帶構件不易從本體部脫離的低體重兒用的紙尿布。[解決手段]一種低體重兒用紙尿布(1)，是具有：至少具備吸收性芯(21a)的吸收體(21)；被配置在較吸收體(21)更靠非肌膚側的外裝薄片(24)；以及帶構件(30)，其中，帶構件(30)，是在帶構件(30)的長邊方向的一方側及另一方側具備卡止構件(31A、31B)，帶構件(30)藉由一方側的卡止構件(31A)在較長邊方向的外裝薄片(24)的外側端(24leo)更靠內側，且，卡止在厚度方向的外裝薄片(24)的非肌膚側的狀態下，吸收性芯(21a)的外側端(21leo)在長邊方向，較外裝薄片(24)的外側端(24leo)與一方側的卡止構件(31A)的外側端(31Aleo)的中間更位於內側。
