A successive forging process of long aluminum and stainless steel plates with an inclined punch was developed to produce a long plate having an inclined cross-section. In this process, the forging load becomes small due to the repeat of local deformation. A side guide and a grooved die were introduced to prevent the curvature of the forged plate. The effects of the forging interval on the deformation behavior of the plate and the forging load were examined. The successive forging process of long plates having an inclined cross-section with a punch having a taper bottom is useful for minimizing waving and depression of the formed plates.