PROBLEM TO BE SOLVED: To prevent a situation that a material of a side seal part is elongated to be torn in an unintended direction without depending on a pattern change of melting junction when peeling the side seal part.SOLUTION: This underpants type disposable diaper includes an easily extensible region 14 which comprises four-layered or below nonwoven fabrics, and wherein each nonwoven fabric constituting at least the front and back faces consists of an easily extensible fabric having load elongation of 4.5% or above at a load of 1 kgf, in at least a part of the longitudinal direction in a side seal part 13. At least the whole width direction, a part in the width direction, or a width-direction inner side adjacent part in the easily extensible region 14 is hardly extended by a hot melt adhesive layer 80 applied to the inner face of the easily extensible nonwoven fabric.
