The present inventors devised methods for efficiently purifying bispecific antibodies using a chromatography column based on the difference in isoelectric points between the H chains of two types of antibodies, wherein the difference is introduced by modifying the amino acids present on the surface of the antibody variable regions of two types of antibodies that constitute a bispecific antibody. Furthermore, the inventors devised methods for efficiently purifying bispecific antibodies using a chromatography column by linking respective antigen binding sites (heavy chain variable regions) to the antibody constant regions having different isoelectric points, and then coexpressing these antibodies.