Provided is a method for bonding metal parts manufactured by splitting longitudinally an end part of a metal plate or a metal rod having a rectangular, polygonal, or elliptical shape, in which the length of incision in the split portion can be freely adjusted and smooth split face can be formed. The metal parts are manufactured by the process comprising the steps of securing a metal plate by pinching both sides thereof with a clamping device, or securing a metal rod by pinching at least two opposite-facing portions on the periphery thereof with a clamping device; splitting longitudinally by slitting or cleaving the metal plate, or the metal rod, by pressing a slitting punch or a cleaving punch against the face of one end of the metal plate, or the metal rod; and advancing the splitting further by repeating the same operation of pressing the same punch stated above against the cleft of the splitting; and is characterized further in that, in each time of the press-splitting operation, the position of the clamping device on at least one side is moved in advance of the next pressing by a stroke corresponding to the distance from one end of the metal plate, or the metal rod, to the distal end of a split-desired portion.