A back region 2 having extensibility in a waist direction and provided with stopper members 5 at both ends in the waist direction, an abdominal region 3 provided with flap portions 6 at both ends in the waist direction, and an absorber 4 that bridges between the back region 2 and the abdominal region 3 are provided. It is set in such a manner that a length W3 of the back region 2 in the waist direction when it is stretched is longer than a length W2 of the abdominal region 3 in the waist direction, and a length W1 of the back region 2 in the waist direction when no force is applied from the outside is almost equal to the length W2 of the abdominal region 3 in the waist direction or shorter than the length in the waist direction.
