PROBLEM TO BE SOLVED: To provide an underpants type disposable diaper which fits well on the thigh roots and nonetheless follows movement of the thighs well and has excellent fitting feeling on the thigh roots.SOLUTION: The underpants type disposable diaper is characterized in that: ends, at leg opening parts LO side, of rear side attaching sites 81s that are attaching sites of a leg root resilient elastic member 81 at both side parts 12A of a back body B are positioned near leg opening parts LO of both side parts 12A of the back body B ends, at leg opening parts LO sides, of front side attaching sites 80s that are attaching sites of a leg root resilient elastic member 80 at both side parts 12A of a front body F are positioned to a waist opening part WO side than ends, at the leg opening parts LO sides, of a rear side part attaching sites 81s and an easily deformable area 85 without leg root part resilient elastic member 80 is formed between the leg root part attaching resilient elastic member 80 and the leg opening part LO in the front body F.
