To maintain, in a wide state, the spaces in a ventilation channel formed when a waist expansion member contracts. This disposable diaper has formed therein, on one or both of a front part (1) and a rear part (2), a cushion part (40). The cushion part (40) includes: an inner sheet (41)； an outer sheet (42)； one or a plurality of waist expansion members (43)； and a cushion forming sheet (44). In a state where the waist expansion member (43) is stretched in the width direction, the member is secured between the inner sheet (41) and the outer sheet (42). The cushion forming sheet (44) overlaps one or both of the inner sheet (41) and the outer sheet (42), and is joined thereto so that in the width direction joining portions (51) and non-joining portions (52) are alternatingly continuous. The joining portions (51) are formed by joining-lines (53) which are straight and extend in the longitudinal direction and at least two columns of which are side by side. The space (second space (D2)) between the joining-line columns in one joining portion is narrower than the space (first space (D1)) between adjacent joining portions.本發明課題在於較寬地確保腰部伸縮構件收縮時所形成的透氣路徑間隔。本發明的拋棄式尿布中，在正面部1與背面部2的兩者或是任一上形成緩衝部40。緩衝部40包含內側片材41、外側片材42、一個或複數個腰部伸縮構件43及緩衝形成片材44。腰部伸縮構件43在沿著寬度方向伸長的狀態下，被固定於內側片材41與外側片材42間。緩衝形成片材44與內側片材41和外側片材42的兩者或任一個重合，且在寬度方向上間隔性地接合，而形成接合部51與非接合部52連續交錯的態樣。接合部51由沿著長度方向延伸的直線狀接合線53並排2行以上形成，接合部內的接合線的行間的間隔(第2間隔D2)比接合部彼此間的間隔(第1間隔D1)窄。
