It is known that it is difficult to bond dissimilar metals such as aluminum and copper or aluminum and iron using diffusion bonding, because an intermetallic compound is easily produced at the bond interface and bonding strength becomes low. However it is possible to bond the dissimilar metals using the vacuum roll bonding which performs hot rolling in a vacuum. In this study, we investigated the effect of bonding temperature and reduction of aluminum plate thickness on bonding strength of Al/Cu clad materials when aluminum-clad copper (Al/Cu clad) materials were produced at 3 Pa in vacuum degree by the vacuum roll bondings. Bond tensile strength of Al/Cu clad materials increased as the reduction was increased. Their fracture types were classified according to the fracture pass, that is, in the base metal of the aluminum, at the bond interface of Al/Cu clad material or in the base metal and/or at the bond interface. Furthermore, the bond interfaces of Al/Cu clad materials were observed using a transmission electron microscope and an electron dispersive spectroscopy. As a result, it was clarified that Al/Cu clad materials are soundly produced using the vacuum roll bonding when thickness of diffusion layer is less than 60 nm even if intermetallic compounds were developed.