Disposable diapers (1) for low-weight children, comprising an absorbent core (2) having a narrow portion in the central part in the longitudinal direction, wherein the central width of the absorbent core (2) in the longitudinal direction is 15 mm or more and 45 mm or less. The length in the longitudinal direction of the diaper (1) in a state where the diaper (1) is deployed and extended in the longitudinal direction is defined as a product length, and after the diaper (1) is deployed and extended in the longitudinal direction, the skin side is placed on the upper surface of the table. If the apparent length of the diaper (1) in the longitudinal direction on which it is placed is the apparent product length, the value obtained by dividing the apparent product length by the product length is 0.7 or more and 1 or less.長手方向の中央部に幅狭部を有する吸収性コア（２）を備え、長手方向における吸収性コア（２）の中央の幅は１５ｍｍ以上４５ｍｍ以下である低体重児用の使い捨ておむつ（１）であり、長手方向に展開かつ伸長した状態のおむつ（１）の長手方向の長さを製品長とし、おむつ（１）を長手方向に展開かつ伸長した後に肌側面を下にして台の上面に載せた自然状態のおむつ（１）の長手方向の長さを見かけ製品長とした場合、見かけ製品長を製品長で除した値は０．７以上１以下であること。
