A disposable diaper (10) arranged on an outside end section in the product width direction in the rear waist area and comprising: a pair of fastening tapes (90) that fasten to the front waist area； and a waist expanding/contracting sheet that straddles the center of the disposable diaper in the product width direction and has expansion/contraction properties in the product width direction. The waist expanding/contracting sheet has a rear-side waist expansion/contraction sheet (85) arranged in a rear-side end section (10R) of the disposable diaper. The rear-side end section (10R) of the disposable diaper has a curved shape whereby the center in the product width direction is recessed more on the inside in the product longitudinal direction than the outside in the product width direction, in the natural state of the disposable diaper.
