Provided is an unfolding-type disposable diaper which has a mutually intersecting length direction and width direction, and in which a first waist section, a crotch section, and a second waist section are aligned from one side in the length direction. The disposable diaper has an absorbent body core and a pair of fastening tapes which extend from the first waist section to the outside on both sides in the width direction. The second waist section has fastening tape engagement ends at the position in the length direction at which the crotch-section-side end of the fastening tapes in the length direction is located when both ends of the disposable diaper in the length direction are aligned. The absorbent body core has, on both ends in the width direction, at least a pair of cutouts. In the length direction, among the region between a product center, which is the center of the disposable diaper, and engagement ends, a section of the absorbent body core where the width thereof is narrowest among the sections of the absorbent body core sandwiched between the pair of cutouts is positioned in a region between the center and the engagement ends of said region.
