[Problems] To prevent a hip cover portion of a back-side outer sheet from swelling and curling [Means for Solving Problems] In an underpants type disposable diaper, a ventral-side outer sheet 12F and a back-side outer sheet 12B are not connected but separated at a crotch portion, the back-side outer sheet 12F has a main unit section 13 that corresponds to joined sections 12A in an up-down direction and a back-side extension section 14 that extends below the back-side main unit section 13, the ventral-side outer sheet 12F is composed of only a ventral-side main unit section that corresponds to the joined sections 12A in the up-down direction, the back-side extension section 14 has a central portion 14M in the width direction overlapping the absorber 20 and hip cover portions 14C extending on both sides of the central portion 14M, in the back-side main unit section 13, first elongated resilient and elastic members 15 are fixed in a state of being extended in the width direction at a predetermined extension ratio second elongated resilient and elastic members 16 are fixed to the hip cover portions 14C in a state of being extended in the width direction at a predetermined extension ratio, fourth elongated resilient and elastic members having high contracting forces are fixed to the lower end portion of the ventral-side outer sheet 12F in a state of being extended in the width direction so that the contraction forces are balanced between the ventral side and back side at the lower ends of the joined section 12A.
