The present invention relates to a peptide excellently capable of binding to a protein capable of binding to insulin (IBP), an adsorbent comprising the aforementioned peptide immobilized on a carrier, an adsorber comprising the aforementioned adsorbent, and a method of adsorbing IBPs by using the aforementioned adsorbent or adsorber. The peptide, adsorbent, adsorber and method provided by the present invention can selectively adsorb and remove IBPs efficiently, and therefore be used, for example, in the treatment of diseases, typically diabetes, in which such IBP acts as an aggravating factor.