A disposable diaper includes: side flaps (14)； pieces of fastening tape (30) respectively arranged on widthwise side portions of the side flaps (14)； and joining portions (40) each of which joins a portion of each piece of the fastening tape (30) to a non-skin side of the side flaps (14) in the thickness direction. In an unfolded state, for each of the pieces of fastening tape (30), a magnitude of force (F1S) applied at a time when the joining portion (40) is peeled off when a region of the fastening tape (30) that is outward in the width direction with respect to the joining portion (40) is pulled in an outward direction along the width directionbeing greater thana minimum value of a magnitude of force (F2S) applied at a time when the joining portion (40) is peeled off when a region of the fastening tape (30) that is inward in the width direction with respect to the joining portion (40) is pulled in any direction between the outward direction along the width direction and an outward direction along the thickness direction.
