PROBLEM TO BE SOLVED: To provide an underpants type disposable diaper capable of more tightly fastening an edge part of an opening, while having a stretch structure in which the edge part of the opening and a part adjacent to the edge part are formed of a same elastic film.SOLUTION: A belly side exterior body 26 and a back side exterior body 27 comprise: basic lamination parts 35 each formed from a leg periphery parts 28 to a part adjacent to the leg periphery part by laminating an elastic film 30 between a first sheet layer 20A and a second sheet layer 20B and folding lamination parts 36 where the elastic film 30 and the first sheet layer 20A and second sheet layer 20B continuous from the basic lamination part 35, and disposed on each leg periphery part 28, are folded outward at an edge 29 of a leg opening. The basic lamination part 35 and the folding lamination part 36 are configured so that the first sheet layer 20A and second sheet layer 20B are jointed at plural joint parts 40 arranged with intervals in a width direction and a fore-and-aft direction, in a state in which the elastic film 30 is stretched in at least the width direction.SELECTED DRAWING: Figure 4
