[Problem] To provide a diaper that can be worn so as to accommodate differences in body sizes of infants (e.g., including premature and underweight infants) and is less likely to hinder treatment and nursing. [Solution] This diaper 2 is provided with: a nonwoven fabric 3 extending from the back side to the abdomen side of an infant through the crotch part； a back sheet 4 for preventing the infant's excretions from soaking through； an absorber 5 that is provided between the nonwoven fabric 3 and the back sheet 4 and absorbs excretions that soak through the nonwoven fabric 3； and a belt part 6 having a joining part 63 that can be detachably joined to the nonwoven fabric 3. At least a part of an area where the nonwoven fabric 3 and the back sheet 4 are mutually adhered does not overlap the absorber 5, and forms an extension part 31 extending from an abdomen-side end part of the absorber 5 further toward the abdomen. In terms of the direction in which the nonwoven fabric 3 extends, the length L1 of the extension part 31 is longer than the length L2 of the connection part 63.
