The disposable diaper (10) includes a sheet-like leg hole stretch unit (100) provided at a side end, in the product widthwise direction (W), of the side flap (70), extending in the product longitudinal direction (L), and being partially stretchable at least in the product longitudinal direction (L). A side edge, in the product widthwise direction (W), of the leg hole stretch unit (100) is in an undulating shape in the product longitudinal direction (L). A distance between the side edge, in the product widthwise direction (W), of the leg hole stretch unit (100) and a center line (CL) changes from the front waistline unit (20) to the back waistline unit (30). The concave unit (140) and the concave unit (160), where an amount of change along the distance starts increasing instead of decreasing, are provided closer to the back waistline unit (30) than a center, in the product longitudinal direction (L), of the disposable diaper.
