[Problem] The purpose of the present invention is to provide a bispecific antibody that is structurally stable, and can show alone a sufficient effect without the co-administration of activated lymphocyte (T-LAK). [Solution] The present invention is therefore related to a humanized highly functional bispecific antibody comprising humanized variable regions of the heavy chain (5H) and the light chain (5L) of an anti-human EGF receptor 1 antibody 528, and humanized variable regions of the heavy chain (OH) and the light chain (OL) of an anti-CD3 antibody OKT3； and having one of the following structures (i) - (vi) in Claim 1, wherein the 5H, 5L, OH and OL have an amino acid sequence represented by SEQ ID Nos 25, 26, 27 and 28, respectively.
