Provided is a method for producing a heteromultimer efficiently and stably by incubating under reducing conditions multiple types of homopolypeptides having a modification in the amino acids that form the interface of the Fc region and/or a modification to destabilize the stability of the heavy chain CH3 region introduced into the heavy chain CH3 region to achieve promotion of dissociation and/or control of association of the Fc region by utilizing charge repulsion.
