Focusing on the fact that antibody molecules with one H chain are not secreted when using the “knobs-into-holes” method, the present inventors revealed that desired bispecific antibodies can be preferentially formed by first expressing the H and L chains of one arm, and then suppressing their expression, followed by expressing the H and L chains of the other arm so that first desired HL molecules (HaLa and HbLb) are constructed, and then the H chains are paired with each other (H2L2). The present invention was thus completed.