The present invention relates to a crystal of a complex of an epidermal growth factor (EGF) and an epidermal growth factor receptor (EGFR), a crystal of a complex of EGFR and a substance regulating EGFR activity, structure coordinates of these crystals, a method for screening for the substance regulating EGFR activity, a method for designing the substance regulating EGFR activity, a method for designing an EGFR variant or an EGF variant, a method for producing an EGFR variant or an EGF variant and an EGF variant or an EGFR variant obtainable by such method, a method for designing an epitope using the structure coordinates of the EGF-EGFR complex, a method for producing an anti-EGFR antibody or an anti-EGF antibody and an antibody obtainable by such method, a polypeptide or a salt thereof comprising a region that forms an EGFR dimerization site, and the like.