The invention relates to a concave extrusion method and an extrusion device suitable for a nonferrous metal. The extrusion method comprises the following steps: enlarging the metal volume in the central zone to form reverse resistance for resisting against metal flow forming shrinkage, that is, to form a centrosymmetric concave curved surface shape in the central zone of the working end face of the conventional biplane round panel shaped dummy block, utilizing the dummy block to form a convex surface at the tail end of the blank to be deformed during the compressional deformation process, and enforcing the change of the metal deformation at the different degrees. The extrusion device comprises an extrusion seat, an extrusion shaft, an inner core shaft, a core shaft sleeve, an extrusion liner, an extrusion die and a concave dummy block. The extrusion method disclosed by the invention is simple and convenient to operate, and capable of eliminating or shortening the forming process of the shrinkage in the center of the rod-like bar, so as to increase the yield of the material and achieve the remarkable economic benefit. The extrusion device disclosed by the invention is simple and reasonable in structural design, convenient in assembling, low in cost, stable and reliable in use, and high in extrusion efficiency and extrusion precision.