A mutant of a potentially therapeutic anti-CD40 antibody is provided which mutant has reduced ADCC and CDC activities designed to be optimized as a pharmaceutical agent. A mutant of an agonistic anti-CD40 antibody, comprising mutation and/or substitution of at least one amino acid in the constant region to reduce the ADCC and/or CDC activities therein, and a mutant of an antagonistic anti-CD40 antibody, comprising at least one mutation or substitution in the constant region to reduce the ADCC and/or CDC activities therein, both mutants having at least a hinge region derived from a human IgG2.