Abstract: A tentative fixing means (4) used for tentatively fixing a stone material (2) to a surface (31) of a concrete form panel (3) before concrete is poured into a form is provided with a bolt (5), a nut (6) and a decorative plate holding member (7). When the nut (6) is screwed on the bolt (5), the stone material (2) is pressed against and fixed to the surface (31) of the form panel by the decorative plate holding member (7). The arm portions (73(1)-73(4)) of the decorative plate holding member (7) are elastically deformable at the decorative plate holding surface (74) of their outer end sections in the nut-screwing direction. Therefore, even when the thickness of the stone materials are different, the stone materials can be pressed against and tentatively fixed to the surface of the form panel reliably by the decorative plate holding member (7).