The present invention relates to a method for suppressing aggregation of polypeptide. Specifically, the present invention relates to a method for suppressing, in a solution comprising an antibody or an Fc region-containing protein, formation of an aggregate derived from an antibody or an Fc region-containing protein having a non-native conformation, the method comprising: the steps of (i) binding an AF.2A1 polypeptide or an analog thereof with an aggregate derived from the antibody or Fc region-containing protein having a non-native conformation in the solution; and (ii) collecting the aggregate bound to the polypeptide or analog thereof from the solution.