A disposable underpants type diaper in which the opposite side edge portionsof the length of leg area can be easily applied tightly around the leg. Belt-shapedmembers (21, 22) traversing the humor absorbing portion (4) in the length of legarea (6) are provided, respectively, at a part close to the front girth area (7)and a part close to the rear girth area (8) on the inner surface of the length of legarea (6) of an underpants type diaper (1). Distal end portions of the belt-shapedmembers (21, 22) are bonded respectively to leakproof portions (43
