PROBLEM TO BE SOLVED: To provide a disposable diaper allowing expansion of a movable area of a belly side part.SOLUTION: This disposal diaper includes: the belly side part wherein an absorber is interposed between a liquid-permeable top sheet and a liquid-impermeable back sheet, and which is positioned on the belly side of a wearer a back side part positioned on the back side and a crotch part positioned between the belly side part and the back side part. The disposal diaper includes: a pair of right and left back side part fixing parts projecting from both side end parts in the width direction of the back side part and belly side fixed parts capable of being detachably locked with the back side part fixing parts, provided on the outer face of the belly side part. The disposable diaper includes a folding part formed on the outer face side of the belly side part, and freely folded and developed. The folding part includes: a front face part formed outside the belly side part and side face parts connecting both end parts in the width direction of the front face part and the belly side part. Fixing parts detachably fixing the side face parts to the belly side part are formed on the outer face side of the side face parts.
