To provide a fastening tape equipped with an extensible material or other fastening elements that are free from excessive extension and contraction of an extensible member, can always keep a suitable degree of extension and contraction, do not therefore generate a disadvantage such as a red mark when they are used for a disposable diaper, and make it possible to easily recognize with eye that the suitable degree of extension and contraction is achieved. In a fastening element for detachably fixing two members, the fastening element is constituted so that it comprises a fastening member having an extensible member incorporating therein an indicator capable of visually showing a degree of extension and contraction.