Abstract: In order to join concrete products to be joined together each having an joining face, an opening formed in the joining face, and an attachment hole communicating with the opening, a junction member body has on its at least one end a swelled protruding portion which is inserted through the opening into the attachment hole. The junction member body further has a plurality of spaces for cleavage extending along the direction of thickness of the junction member body, each of the spaces for cleavage being cleaved open by an external force caused by an earthquake or the like, to present satisfactory extensibility and collapsibility.