[Problem] To provide an anti-human Igβ antibody in which BCR and FcγRIIb are crosslinked and which has a more enhanced immunosuppressive function compared to conventional antibodies.[Solution] An anti-human Igβ antibody including: a heavy-chain variable region that includes a CDR 1 comprising an amino acid sequence from amino acid numbers 31-35 of SEQ ID NO: 2, a CDR 2 comprising an amino acid sequence from amino acid numbers 50-65 of SEQ ID NO: 2, and a CDR 3 comprising an amino acid sequence from amino acid numbers 98-108 of SEQ ID NO: 2； a light-chain variable region that includes a CDR 1 comprising an amino acid sequence from amino acid numbers 24-38 of SEQ ID NO: 4, a CDR 2 comprising an amino acid sequence from amino acid numbers 54-60 of SEQ ID NO: 4, and a CDR 3 comprising an animo acid sequence from amino acid numbers 93-101 of SEQ ID NO: 4； and a heavy-chain constant region, said region being a human Igγ1 constant region having S239D, H268D, and L328W amino acid variations.
