To provide a method where, in a method for producing a clad material in which, regarding a plurality of metal plates with different materials, the respective joining faces are surface-cleaned by pretreatment, and thereafter, the joining faces are made to adhere them to each other, so as to be rolled and press-welded, the joining faces of the metal plates can be effectively surface-cleaned without using an alkali solvent and a metal brush.

As the pretreatment method for the joining faces of metal plates, to the joining faces of the metal plates, a cavitation jet is jetted parallely to the metal plates, thus the joining faces of the metal plates are surface-cleaned.