The purpose of the present invention is to provide fragments of humanized anti-EGFR antibody substituted-lysine light-chain or heavy-chain variable regions, and single-chain antibodies, etc, comprising the same, having sufficient binding activity (affinity) with target cells, and having the ability to undergo various site-specific and uniform chemical modifications. The present invention pertains to a humanized variable region on the light-chain or heavy-chain of antibody 528 against human epidermal cell growth factor receptor 1 (Her-1), said variable region comprising the amino acid sequence represented by SEQ ID NO: 2 or SEQ ID NO: 4, wherein fragments of humanized anti-EGFR antibody lysine-substituted light-chain variable regions are formed by substituting a different amino acid for all of the lysine residues, or all of the lysine residues except for the lysine residue(s) of one specified moiety.
