Basic Characteristic of mechanical bonding process using divided plastic flow is investigated in this paper. This bonding process can be applicable to the bonding of any combination metals such as bonding of aluminum and steel. It could be utilized not only to join structural steels but also to manufacture clad sheet continuously within rolling process. Basic characteristic of proposed bonding process is investigated through a series of bonding experiments using aluminum alloy and plain carbon steel, and effects of geometries of bonding part on divided plastic flow and bonding strength are clarified. Through the investigation, it has become clear that sound bonding of aluminum alloys and steel can be realized under cold forming temperature. Better bonding characteristics could be obtained if we optimize geometry of bonding part.