A three-dimensional workpiece including a first ductile plate, a second ductile plate and a core layer is provided. The core layer is located between the first ductile plate and the second ductile plate. The first ductile plate, the second ductile plate and the core layer are bound together and have a three-dimensional shape. The first ductile plate has a flat area and a curved area. The core layer has a core flat area and a core curved area. The core flat area is superposed with the plate flat area and the core curved area is superposed with the plate curved area.