A patent was issued for a disposable pant-type diaper comprising a front portion, a back portion, and a crotch portion which is positioned between the front and back portions, in which a waist opening and a pair of leg openings are formed by joining both longitudinal side-edge parts of the front and back portions which face each other, and a stretchable elastic member is disposed along at least a part of each opening, wherein a cutout portion is formed in a part of the side-edge part of one of the front and back portions so that only the front and back portions assume a non-joining state at the side-edge part on which the cutout portion is formed, and wherein an adjusting tape is arranged on the cutout portion so that one end part of the adjusting tape is attached on a non-joining part of the side-edge part of one of the front and back portions without the cutout portion formed therein, the non-joining part on which the one end of the adjusting tape is attached being exposed by forming the cutout portion, the other end region of the adjusting tape having fastening means detachably fastened to one of the front and back portions on which the cutout portion is formed.