A disposable diaper having a longitudinal direction and a width direction intersecting with the longitudinal direction, the disposable diaper having a central band-shaped region including an absorbent body for absorbing liquid, side flaps positioned on both sides in the width direction of the central band-shaped region, and band-shaped leg-surrounding elastic sheets for expanding and contracting along the longitudinal direction, the leg-surrounding elastic sheets being provided to the side flaps. Edge parts on the outer sides of the side flaps in the width direction are provided with wavy portions in which projections convex toward the outer side in the width direction and recesses concave toward the outer side in the width direction repeat in alternating fashion in the longitudinal direction, and the leg-surrounding elastic sheets are disposed on the inner side in the width direction relative to the recesses of the side flaps.
