A disposable diaper having a front-rear direction and a width direction that is orthogonal to the front-rear direction, includes: a front waistline region; a rear waistline region; a crotch region disposed between the front waistline region and the rear waistline region; an absorbent core; a skin surface side sheet disposed on a skin facing surface side from the absorbent core; a waistband disposed on the skin facing surface side of the skin surface side sheet in the rear waistline region; and a fastening tape disposed in the rear waistline region and that includes a locking portion.