A corrugation forming apparatus includes, as forming members, a rack tool assembled to a slide table and a pinion tool which rotates with rotation of a shaft. The apparatus also includes, as a displacement synchronization mechanism, a feed rack integrally assembled to the table and a feed pinion gear in meshing engagement with the feed rack. When a handle is rotated, its rotational force is transmitted to the feed rack via the feed pinion gear, so that the rack tool moves along the axial direction, and the pinion tool rotates in synchronism with the movement of the rack tool. This enables forming of successive recesses and projections on the thin metal plate, while reducing ductile cracks and warpage.